hmmmmm........name change

OK, so 3 times in the last 2 weeks DD has told me (she is 6) that she wants to change her name so that she has her dads last name and the same last name as her brother and sister (they have different dads, i am remarried with the same last name as my younger 2).
I have explained to her that we need to speak to her dad about it, and explained that we dont want to hurt his feelings or make him upset.
My question is, do I bring it up with him or should I leave it until she talks to him about it? I want to make it clear that it is entirely her idea, and I havent emphasised the point at all.
We have 50/50 custody, and are on pretty amicable speaking terms
TIA

Id do something like that too. Approach him and say that DD and said this out of the blue. Wanted to warn you in case she brings it up with you so you aren't caught off guard with it. If you are ok with it either way then I'd also let him know this and that you don't want to push him aside or make him feel that way etc.

Caitlyn had her biological dad, who im on good terms with, surname and my maiden name , hyphenated with mine at the end , when I married we unofficially made my husbands surname the last one but left her bio dad's name first .
I just explained to C that this way she has both dad's and both sets of siblings names ,so she is linked to both .

If you're ex and you are on good terms , you might find that he is ok with the idea , if you tell him your daughter's reasons