Changing your children’s names:
You must have custody of your children if you want to file a name change
on their behalf. You follow the same procedure as changing your own
name (see above).
If you do not live with the child’s other parent, you
must send a copy of the petition to change the children’s names to the other
parent by certified mail in addition to publishing the notice in the paper. If
you do not know that parent’s current address, send the letter certified to
the last known address. The post office will return the letter to you if it
cannot be delivered. DO NOT OPEN THE RETURNED LETTER. File it
with the court.
If the other parent receives the certified letter, the post
office will return a green card to you. File the card with the court.
If the other parent objects to changing the children’s names:
The court will decide based on what it believes to be in the children’s best
interest. Some courts look at the parent’s relationship with the children,
whether the parent pays child support on a regular basis, and the harm
caused to their relationship if the name is changed. BE PREPARED to
provide the court with valid reasons why it would be better for the
children’s name to change. The court will not grant the name change
simply because the parents do not get along or because one parent has
remarried or changed their name.
http://www.masslegalhelp.org/uploads...ge-booklet.pdf