Adding another last name

What is the name of your state? WI

Unsure if this is where to post this question but here goes.
I have 3 kids, 2 with their fathers last name ( my ex husband) and my youngest has my current husbands last name.

The older kids want to use my current husbands last name but my ex will not go for an adoption. I do have full legal custody of the 2 oldest kids.

Is there a way I can legally add my husbands last name to the older kids last names?

Thanks,
PaulieMJK

[nextwife]

Only if you are able to get a court order allowing this.

My ex is in Canada and I am in the USA.
How would I have to go about getting a court order to allow this?

The school system here has allowed the kids to use my husbands last name since we started but now that my eldest is starting high school they say the legalities are she has to use her fathers name.

This has devestated her.
Is there any way we can hyphenate both names without getting a court order?

Again, I have full physical & custodial rights.

[tigger22472]

You would still have to get bio-father's permission to get the name change. If he were to find out that the children were using your husband's last name in school you could be looking at some serious problems.

Just for clerification, they were using both... Thiers-Newhubbys

Thanks for the opinions... much appreciated!

PaulieMJK