Children's Name Change

[MommyofTwins]

New Jersey- I am a single mother of 2 year old twin girls. I was never married to their father but I gave them his last name. He provides weekly child support to me but we have no legal agreements. I would like to know if I get legally married in the future how can I add my new married last name to my daughter's last name without eliminating their name now?

Also, what are the legalities of custody for each parent if the parents were unmarried like us and the children live with me? He has never asked me for custody of them, that is why I never filed any custody papers.

Should I?

Thanks.

[stealth2]

You'll get better feedback if you repost your question to an active board rather than an archive such as this one.