Or do they tend to wrap up their identity in being something/someone to other people's children?
I'm not talking about if mom is violent or abusive or downright nasty, but...
If the parents don't want you opinion on certain decisions why is that really a big deal?
If mom requests you not do certain things with the children because she wants to do it, why get upset?
If someone got married to be a SM I could see getting upset, but if you got married because you love your husbnd and wanted to be his wife I wonder why letting the parents handle their kids, parent their kids, deal with their kids, make decisions for their kids that do not include the SM are things to get upset over.
If mom was in your marriage in some way, attempting to treat your man like her man still (calling for every little thing, wanting his help for things not kid related), telling you what he likes/doesn't like, etc I don't think many wives would like that because that is THEIR marriage. And most want mom out of that (can't blame them). So if you feel that way about your marriage, you take care of it, it is your business, not moms...why get upset when mom feels that way about her children and SM? IF mom is taking care of her kids and other normal disclaimers apply.