My daughter was married to husband no 1 had 2 children and then divorced and married a man who had 3 children..The two boys are still her children but you have to go to her ex-husband to find them Why aren't they with her.and why does it have her 3 step children as hers

Might be stupid question but there were huge problems in my mothers family when grandma remarried and they just assumed their step fathers name and they actually did not exist Big trouble with the wills.