There's a difference between maintaining good relations with an ex with whom you share children, and being enmeshed to the degree that a future partner feels that there is insufficient room for them in the relationship, and starts to feel threatened, as you have done. Do you live together? If not, don't move in, is my advice.  He needs to develop better boundaries, and until he does, yours and his relationship can't progress. If you do live together, think seriously about whether he is ever going to be available to you in the way most partners need.  Most of us wouldn't be able to tolerate the situation you describe, nor is it reasonable for him to expect you to. 

I agree that this isnt right.  Perhaps they havent been divorced very long.  And, I understand him wanting to keep relations civil.  But there's a difference between civil and discussions of dating and her personal life.  One time, I read another post on here with a similar question and someone responded that the man hadn't established his life as a single dad yet, ie, a man who parents his child and has that all worked out and who then is ready to incorporate a new relationship in his life.  Your BF might not have done this work yet which also includes a new, different mode with the ex.

and stepdad trying to make her relevant in our marriage but hubby zoned out and never told them to shut it!!

it was only 9 months ago he finally told off eldest sd that she had no manners and it was extremely rude and disrespectful of her to rant on bs about bio mum and stepdad. That hubby is married to me, i am his wife and he cares about me, not their mum so she needs to stop this nonsense. 

She so called apologized by saying she is sorry if she did anything wrong (meaning she didn’t feel she did anything wrong), no doubt she reported this exchange to bio mum who was fuming and its been 9 months of no contact with sd’s and their dad as they’re sulking that stepmum is the one hubby loves and has feeling for and not the psycho exwife.

So - he doesn't call her as well and vent to her about his personal life, he just listens to her? To me, that means she still sees him as "hers" vs, they are "friends", since friendships usually go both ways.  It's reasonable for him to tell her that now that he's dating someone, he won't be able to be a sounding board for her personal issues - it will be interesting to see how she reacts.  Seems to me if she were a healthy person, she wouldn't still be using her ex-husband to vent to, so there is a chance her true (and crazy) colors will be shown if he set limits.  Still worth it to do, though.

I know that my ex-H and I went through many phases after our divorce, as we tried to figure out our relationship since we have 3 kids together. We were never enmeshed, and I told him very little about my personal life. However he went through a brief phase where he thought it would be cool if his ex-wife could give him advice about women/dating. Of course this was well before DH and I were married (just started dating I think). So to me this is a conversation with him, not an automatic walk away. It does not mean he won't distance himself from her as he's committed to you. At least for us, this meant nothing. I had moved on.

Paige- I say this with all sincerity - you should seriously consider breaking up with this guy.  I'm much older and also "dated" a guy with a 5 year old.  He also listened and was "friends" with BM for many years, never ever challenging dysfunctional behavior by SD.  
 

I married "that guy" and it's been 29 years.  Sad to say I often wish I had not because of ALL the stress and heartache from trying to blend our 2 families and me living with a "shadow" family and shadow wife!  Now my 36 year old SD is the shadow wife!! 

These things don't usually get better - they can get much worse.  A five-year old is adorable and sweet, a sullen 14 year old not so much, a pregnant 16 year old - horrible, a 22 year old with 2 kids and no partner and job - who quits high school- makes life Crazy!!  That's what's possible in your future - that's my life!  And my DH has often put this first daughter first emotionally and her BM - esp during the 15-25 years of her life with her 2 young kids that we essentially paid 75% of their living expenses.  Life can get REAL very fast my young poster...

So my sincere advice is you've only dated this guy for one year - cut your losses quickly.  Move on and  SAVE your future self YEARS of heartache, jealousy, envy, frustration and fights with this man.  He is not the only guy for you.  There are plenty of loving men who are "free" without this previous family baggage. Find those guys and give yourself a chance to have your own family and husband who focus solely on you and your kids- not his previous Shadow wife and family!!

My dear dad warned me to do the same when I was 29 and dating my now husband.  I really should have listened to his wise words!

She doesn't have any friends to vent to?

They are still emotionally enmeshed.

Not only that, but he just brushes aside your concerns and has no respect for your feelings or the relationship that he's now in. He is more concerned with what he thinks would be rude to his ex, than he is about disrespecting and being rude to his current GF.

Does he enjoy hearing about her personal life? Is he worried that she will become high conflict if he doesn't indulge her?

Any normal person would understand that it's crossing a line to talk to your ex about your love life when the ex is in a relationship. This type of enmeshment keeps people from truly moving on and is part of what can lead to exes getting back together.

He is not ready for a relationship if he can't set some boundaries with her. He's not ready for a relationship if he won't listen to your completely reasonable concerns.

And really, if this is something that he is not willing to have a conversation about and come to the realization that it's over the top, if it's not something that he is willing to stop, on his own, forcing it will not do a bit of good.

I hope the two of you work it out before you've invested too much more time. By that, I mean, I hope he either comes to his senses, or you have the strength to do what YOU need to do for you.

I'd reconsider this relationship if boundaries can't be put into place. Co-parenting is great. However, they should only be discussing the child. If she is discussing dates/boyfriends, etc. I'm sure he is also venting about you. Totally inapproriate. It seems they are still emotionally dependent on each other. Do you really want a partner that drops what he is doing anytime just to "chat and catch-up" with BM? I don't think he can be fully invested in a relationship with you, if he still has that going on with his ex.

My DHs BM was totally like this when we started dating. She wanted to hang out with DH and SD together. Talked about boy problems, etc. I honestly felt like she used "co-parenting" as an excuse to try to "win him back." DH had to put his foot down. He was almost blind to it, until I pointed out women have motives... Then he started to see it for himself. 

I personally think both your BF and BM are living in the past. 

Unless you also have friendly relationships with your exes, I would insist and better boundaries and give it a firm timeline in your own head to see that change. A matter of months would be sufficient. After that, I would consider leaving.

I went through something very similar with my ex-BF. Because I was child-free with no baggage, I asked for stronger boundaries with his ex, who he had a very similar relationship with (five years post-divorce). I never saw the change; he just wasn't a guy who could put his foot down with anything. And that is the worst-possible kind of dad you could deal with. I ended it right around the one-year mark. So happy I did and wish I had wasted less time and frustration with him.

Good advice all around from everyone in this thread.  He needs to establish boundaries.  I wish I had found this place when I first moved in with my DH.  BM was emailing him all the time with articles that he would be interested in and asking for advice.  At the same time, she was also falsifying medical bills so that he would over pay and charging extra curriculars about 3 and 4 times for the same activity.  He just trusted and paid and was broke.  She was determined to squeeze every dime out of him, keep him as an emotional outlet for herself, and then bad mouth him to the kids and alienate them.  It was mind-blowing that people are like this.  It didn't take long for him to understand once we started discussing.  I knew something was wrong when I was ignored every time the stepkids were at our house.  I told him that I would not stand for it.  I think he felt like he was sparing their feelings in some way, but he wasn't.  He did put boundaries in place, and I took over the finances.  From that point on, a receipt and EOB was needed for any extra medical expenses.  He started saving about $500 a month from me taking control of the finances alone.  She imploded, but who gives a $#%$.

Your BF might be under the mistaken impression, like I was, that he could have a friendly divorce.  That's what I naively thought, that we would navigate the whole divorce journey and still maintain a cordial relationship.  I thought it would be less harmful to the kids.  That was before my ex tried to kill me, kidnapped my son from school, stole my car and stalked me.  That was before I was carrying one of my mother's kitchen knives in my purse with the intent to stab him if he got close enough.  I'm not saying your BFs situation will get this bad but bottom line, once you divorce a person, the relationship changes, like it or not.  He might still be having those "Im a nice guy having a friendly divorce" thoughts and that's keeping him from establishing a more appropriate response to her.

You phrased your question "how to be comfortable" with their coziness with each other. But you shouldn't be comfortable with it.

His enmeshment with his ex is a red flag, and if he's making you think your discomfort with it is the problem, that's a second red flag.

Everything tog said, she's using him as her go to until or unless she properly replaces him. I had 2 to 3 yrs of such crap. Its not normal and its not acceptable. If its not about handover of skids or anything to do with them then jog on bm, he's not her shoulder to lean on 

Xs have zero business being enmeshed at all.  Even if they have created failed family breeding experiments.

The only interface that former breeding partner Xs have any business having is minimal and limited only to brief discussions and actions in raising their joint children. If they choose to maintain a close personal relastionship then neither of them have any business being involved with a new partner.

IMHO of course.

I would not have a partner who was close to their X, particularly one they had spawned with.  I suppose that is because I may not be as evolved as some. But ... an X is an X for a reason and has no place in future relationships of their former partner.