Legal Question in Family Law in California

Your ex husband is her legal father, at least as of now. If he consents you can change her name to anything you want. That would also not impact SSI at all. SSI is based on legal paternity There is a legal presumption that a child born to a married couple who are cohabitating at the time of conception and the man is not impotent is a child of the marriage. That presumption stands unless distubed by a court proceeding. So, I can't say with absoute certainty without doing legal research that is beyond the scope of a free question, but I can see no reason there should be issues with the SSI benefits paid to date. As for going forward, however, it sounds like you guys really need to do a paternity action and get the biological father made the legal father. A mere name change will not do that, and will not give him and her any rights regarding each other. If you died in a car crash, for example, the biological father would have no right to take care of her. And if he dies she will have no rights of inheritance or any other survivor rights. Those are just a couple of examples of what will be missing in their legal relationship if you do nothing but change her name.