It sounds like your bf is a "Disney dad". I am sorry. 

If you have successful adult kids, why tie yourself to a guy who is poor parent, and has young children who have behavioral issues?

Find a guy who is in your stage of life and who has a healthy relationship with his adult kids.

Co-parenting in its simpliest form is: To share the duties of raising (a child) (used especially of parents who are separated or not in a relationship).  It is a term generally reserved for the parents of the child, mom and dad.  I don't think mom was mentioned above?

You mentioned both kids were diagnosed with Autistic Spectrum disorders.  They are also quite young.  This makes what appears to be a complicated step-situation even more complicated.  With this disorder, these kids should be getting some type of assistance outside the home, as they can certainly go on to become well functioning adults, but with professional assistance.

I get the feeling your BF is feeling very overwhelmed with these kids and just "throwing food at 'em," so to speak, to do what he has to do and move on to the rest of his day.  So, where is BM in all of this?  Is dad getting the professional help he needs?  Ordinarily, I'd say a big Yes! to dad teaching them all kids of manners, but it can be tricky with Autism and this is where he needs direction from and should be following the lead of professionals.

Given that, it is difficult to compare your successful adult children to his young children, so I would avoid making that comparison until you know more about their disabilities.  Yet, I also find myself agreeing with tog redux above on some level.  Step-situations are usually difficult enough with those who are close to our "relationship equal," simply meaning both BF/ GF are divorced, both have adult children, etc.  So, by going outside your relationship equal you have added another layer of complexity to your relationship.

I guess my advice for you is as it would be for all SMs:  Date this guy, without moving into the home, keeping both of your eyes open and realize that as your relationship may progress, very little of your DH's relationship with his kids will change.  Is that something you can live with?

Kids on the spectrum are different, as you well know. One thing with my SS20 who is autistic is that I give him a chance to re-word something to me. I will stop the conversation- look him in the eye and say "Try again- this time use your manners/drop the attitude/check your tone/____" - He isn't being rude on purpose and he doesn't understand social cues so he messes up... a lot.

It isn't that he CAN'T do better, he has to be reminded. 

As for your husband, he needs to start setting those routines. Kids and adults with ASD need routine. They need expectations, goals, etc- just like every other kid. If you husband isn't willing to do that- knowing what I know now- I would leave the relationship. 

My SS won't ever live on his own. He is only level 1 but borderline to level 2. He is considered high functioning but doesn't have the sense to not stand out side mid hurricane for goodness sakes. He can't prepare his own food. He has to have a job coach to work. He doesn't have any self care without us fussing daily. It is exhausting.

My only reprieve is that my husband is such a good dad. He never makes me be the bad guy. He backs me up no matter what and if he actually disagreed with me he tells me in private later with a gentle - I would have done it this way ____, next time lets try that, ok? 

If he wasn't the man, husband and father he is, I couldn't do this. 

Who has full custody?

My first thought was, do they do this at school? OR is their behavior only at dads?

Does BM have the very same problems at her house?

Here I have copied and pasted Wikipedia for ya!!

Coparenting

From Wikipedia, the free encyclopedia

Co-parenting is an enterprise undertaken by two or more adults who together take on the socialization, care, and upbringing of children for whom they share responsibility[1] Coparents may include a variety of configurations, including a mother and a father, two mothers, two fathers, a parent with an adult sibling or grandparent, or a parent and another adult relative. The coparent relationship differs from an intimate relationship between adults in that it focuses solely on the child.[2] The equivalent term in evolutionary biology is biparental care, where parental investment is provided by both the mother and father.[3][4]

The original meaning of co-parenting was mostly related to nuclear families. However, since the United Nations Convention on the Rights of the Child, 20 November 1989, the principle that a child has to continue to maintain a strong relationship with both parents, even if separated, has become a more recognized right. Thus, the concept of co-parenting was extended to divorced and separated parents and to parents who have never lived together.[5]

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I must say, If I was divorced with grown adult kids there is NO way I would hook up with a guy who had young kids. He must be really amazing for you to consider this a good situation.

Around here co-parenting is often contrasted against paralel parenting.

Co-parenting is usually to do with the separated/divorced parents actively and cooperatively parenting the child. They will coordinte together to work out what is best for the child. Of course ex's are not always perfect, but when two reasonable people can get over the reasons for them not having a relationship with each other any longer and are happy to accept the existance of the other parent in their child's life this is the ideal senario. 

Paralel parenting is usually a method of parenting where the two bio-parents run different housholds and do not attempt to co-ordinate beyond absolute necessities/emergencies. This usually becomes necessary if co-parenting is not going to be succesful due to one parent actively trying to undermine/sabotage or otherwise be difficult with their ex. 

Co-parents might inform each other of important updates from the school and attend a parent-teacher conference together and then work together to find a way to help little Jimmy to stop being disruptive in class and get him some extra help in math. 

Paralel parents would each get their own information from the school (as they are each entitiled to), try to arrange separate conferences with the teacher (if the school with do this) and then each work individually on helping Jimmy in their own way on their own custody time without coordinating. 

The advantage of paralel parenting is that it reduces the contact between the ex's and can help to subsequently reduce the friction and constant unwanted intrusions into each others lives.

As for the situation with your boyfriend, if he has no desire to make changes to his parenting or home life to help his kids develop and meet their special needs then the situation is unlikely to improve. You could come in as girlfriend/future life partner and try to implement changes and take over parenting, but it will likely blow up in your face and not be apprechiated by anyone. Some people just aren't great parents and are not interested in learning and changing to become better parents. It is not fun to be around their kids.

A "coparenting relationship" is when you get along with, hang out with, and prioritize the needs of your ex after a divorce more so than you did when you were married. You are friendly, talking and texting several times per day, and hanging out together regularly. You do this to prove what an awesome parent you are even though you are divorced, and to reassure yourself that you are completely in control of your kids, even when they are with the other parent. It makes you feel good about yourself to know that your ex likes you so much. You base your entire identity around being the parent that is fun and whose house the kids want to be at most, because your whole identity is wrapped up in being an "awesome parent", and it's all for the kids. Your ex comes to all your family gatherings and is closer to your parents and siblings now than when you were married. You don't need a custody schedule, because you are all always together anyway. Just decide on a daily basis who sleeps where. It's for the kids!

Note: the above paragraph is complete BS, and if a divorced parent tells you anything of the sort, run. That is enmeshment disguised as a "good coparenting relationship." 

Coparenting is about a couple parenting as equity parents to any children in their home regardless of kid biology.  IMHO of course.  The blended family opposition parent has their own home and parents in their home with their own partner.  If the blended family opposition bio parent is toxic and unreasonable in their interface with the other half of the blended family then they have zero influence in the parenting that goes on in the other half of the equation and their shit should not bet tolerated.

That is why, if they are not reasonble, I don't give a crap about anything that the blended family opposition has to say about anything. Period. Dot.