Surname thoughts

[Throughgrittedteeth]

DP are expecting our first DC together. Both of us have a DC from a previous relationship - I have a DS and he has a DD.
My DS's surname uses both mine and my exes names together and DP's DD uses just his surname.
I just wanted some external thoughts on what you would do with new baby's surname. We are going to get married eventually and I plan on keeping my surname, in part because DS has my name, but also because I like it.
Logic tells me it should be something like "New baby my surname his surname". Any thoughts?

There is no one way to solve this problem.

Our solution was-
Me: carmenta MySurname
DH: DH HisSurname
DD1: DD1name HisSurname MySurname
DD2: DD2name MySurname HisSurname

It's not perfect but double-barrelling our names would sound daft. I didn't find out until recently that some people pick a family name from somewhere in their shared tree and all change to that so the whole family has the same name, which we would probably do if we started over.

Thanks for your reply. I think if neither of us had other DC it would be pretty simple as I would happily take DP's surname. I was quite pig headed about my DS's surname and wouldn't shift on him having mine in there quite proud now as I knew deep down that my relationship with my ex wouldn't work out.
I would still like this DC to have some link to me and it's brother but equally a link to DP and it's sister!

I think perhaps what I said originally is probably the simplest way of keeping us all happy.

Incidentally DP hasn't given his opinion on any of this, which is why I'm musing on here

Definitely new baby your surname his surname! Or the other way around. Or you can merge them, if it sounds good.