So, my SS brought home a drawing he did in school last week and it had him, his brother, his dad and his mom all holding hands and then I was up in the corner with his mothers boyfriend. When I asked him why I was so far away he said "because you are not really in our family" I was so hurt. When I met their father, these two boys were 4 and 5 and so incredibly broken. BM would lock them either in their rooms or out of hers for hours at a time while dad was at work so she could smoke weed, practice tattooing and watch Netflix while cheating on him - she did this from the time they were born until the divorce. When I first started dating their dad, she had nothing to do with them for 6 months. Eventuallly when she realized I wasn't going anywhere, she decided it was time to be mother of the year. It has been almost a year now since she started seeing them kind of regularly, as long it is convenient for her to be a parent at that time. It has taken me almost 2 years to get them to be normally functioning, trusting children. I know he is only 7, but it hurt so bad to hear him say that. I guess I'm just venting. This woman almost destroyed her sons. If anyone isn't part of the family it is her.

Re: "not part of our family"
Look on the bright side of things. He feels you are a big enough part of his family to draw you in.
Kids are very literal, they don't understand always the nuances to the titles and therefore in his head mom+dad+sibling = family....it's not until a little older and more life experience that some kids learn that blood doesn't necessarily = nurturing+their best interests and family.
We probably all have friends that are more "family" than some of out blood relations.
It just takes a little time, it hurts and stings, but try to remember his age and just continue doing what your doing and he'll get it.
Is it possible that the teacher specifically told them to do mom+dad+kids?
If DS is given no guidance, he will draw his family as me, DH (not his biological father) and his sister. Sometimes he adds our dog. Never the cat.
But when he was younger, if he'd been told to do mom+dad, I think he would have been really confused.
It's going to take longer than that for these boys to heal. And I know it's easy for you to feel hurt (that's a very real and understandable feeling) but the facts are, that woman is still their mother and regardless of how she treated them, they are going to spend the rest of their lives searching for her love and acceptance. Especially if she keeps dangling it and pulling away like she has.
My husband has a mother like that and he's really screwed up still at 50. SO I have some advice. Know that these little boys minds are a little confused to give yourself some comfort. But be the best mom and loving female/mother figure to them that you can be without conditions or expecting anything in return. Even if you don't marry this guy, they will remember how loving and wonderful you were and you will leave some good with them, to hopefully counter the bad that she has left with them. And if the relationship lasts - you will be the one that will fill the hole their mother left. It won't be easy. You're in for some tough times, but know that if you stay loving and strong, they eventually will be too.
Good luck to you.
I know how much it hurts when these things are said. My skids have brought home "family" pictures without me before, and yeah my feelings were really hurt.
But I think you need to take a step back and let it go. I doubt he did it intentionally to spite you. Biological ties are serious business; little kids will love their mommy no matter what in most cases. It's possible he sees other kids in his class with "normal" families, and he's grieving the loss of that in his life.
After you calm down, maybe you can talk to him about what makes up a family and he's lucky to have extra people in his life to love him.
I think this is very important to remember, too.
Oh my heart goes out to you. My "step son" (I am partnered but not married) has been in my life for 6.5 years starting when he was 4. His older sister (then 11 now 17) accepted me with open heart right away, as my son accepted his father/my partner (DS and SS are same age)...but SS is a different kind of kid (and has different trauma). Some days I feel like this kid is never going to accept me, and it's painful, but I don't think he means to hurt me...it's just that his way of accepting me is going to be on his terms not mine. So I really try to meet him where he is at, show interest in the things that he cares about (though he will probably never reciprocate) and love him for the child that he is. Unconditional love is just that.
And a marriage certificate is not going to change his behavior towards me...nor is gestating his half-sibling. Time and maturity, one can hope. We have our moments, so I cherish them - however small.