
Quoting
Xena
Once he has been declared the legal father the legal ground that he has for petitoning for a name change is that he is the father with rights.
Petitioning for something, and winning are 2 different things. However, given the very young age of your children, it is more likely that a Judge would order a name change. The best thing to do in that situation would be if you are willing to agree, or to have the names hyphenated- mom's name-dad's name.
BTW- he is not a sperm donor, he is the father- big difference inthe two. especially when the father is apparently wanting to be a part of his 5 month old children's lives. You and him will need to get along for the next 18 yrs or so for your children's sakes, so you really should begin that now by calling him the father rather than the sperm donor.