I have been married to DH for 12 years, he came into our lives when my children were 9 and 12. He has supported them in every way, they adore him and he them. They are still super close into adulthood.
My MIL/FIL and DH siblings have never had much to do with my kids. Probably seen them about 5 times in the whole time we've been together. She says she can not accept them as part of her family as they are not blood related, therefore not her grandchildren, and I think the rest of the family follow suit for a quiet life.
She also has told DH many times that he can't possibly know what it's like to be a parent as they are not blood related to him so it's not the same.
I have become numb to this narrative as I have heard it so many times. But on a recent catch up she had with DH she said it all again and I just don't get it. How can she not acknowledge them and everything her DS has done to support them and not be proud of that?