My advice is imagine living with his kids every day 24/7. Could you do it? If not, you should not marry or move in with this man. When you live with a man with kids, that possibility is always there. I started out only seeing my SDs during the summer and holidays. Now she lives here all year long except for 8 weeks that she visits her BM.

If I had inown I would be the full time caregiver for SD, I am not sure that I would have jumped into this relationship. And compared to so many women on here, my SD is a breeze. But having her here full time has changed my routines and limited my possibilities.

Yes, it can work, but only if the two parents agree on parenting issues (you guys don't seem to).  I'm a bit confused on why you are jealous of time spent with his kids when you have your own?

It has worked for us for 24+ years.  However, our blended family formula is relatively simple compared to many. 

I am a non breeding Sparent. My bride brought the kid to our marriage.  We met when SS-26 was 15mos old and married the week before he turned 2yo.  He is an only child in our family.  I was the first person SS ever called Dad(dy).  We didn't require that, he chose to do that on his own a few months after we started dating.  So I have pretty much always been dad and I raised him as my own.

My wife had full physical and legal custody while the SpermIdiot had 7wks of long distance visitation. 5wks summer, 1wk winter, 1wk spring.

In an equity life partnership, nothing comes before the marriage or the spouse. Including kids.  Ever.  Kids are the top marital responsibility but never do they take priority over marriage.  Part of equity life partnership is that both partners are equity parents to any children in the home regardless of kid biology. 

In our case my bride and I partnered to ensure and protect SS's best interests from the toxic manipulation of the the toothless manipulative moron SpermClan at the shallow and polluted end of his gene pool. 

We successfully raised SS-26 to viable adulthood and prepared him to protect himself from his toxic SpermClan as an adult.  We kept him abreast of the facts regarding the entire blended family picture in an age appropriate manner as he grew up.  We reviewed the CO with him, the entire contents of our Custody/Visitation/Support files with him, court records, SpermClan arrest records, divorces, etc, etc, etc..... We reviewed CS with him and kept him up to speed on the comprehensive picture so that he could counter the manipulations of the SpermClan when he was on SpermLand visitation.  

SS-26 asked me to adopt him when he was 22.  We made that happen. So now we have papers clearly making official what has always been the case. I'm his dad. 

So, yes. It can work.  It takes work, it takes an equity life partnership at the core of the blended family, it takes both partners being equity parents to any children in the mix regardless of kid biology, it takes the establishment and enforcement of reasonable standards of behavior for kids in the home, it takes the application of effective consequences for any choice to deviate from the stipulated household standards of behavior, it takes making the marriage and each other the only top priority.

Good luck.