How do I tell him ?

So my SO loves the name CARTER for our baby boy, the only problem is that my first love has a son by the same name.

To give further context the mother of his child is also the girl I caught him ( my first love ) cheating... and we got into a pretty brutal fight about it ( her being on the losing end)...me and him have since remained friends after falling out for a few years. ( this happened when we were teenagers)

My first love and members of my family are still close because we all grew up together, my cousin is even his sons god father. Their kids play together and eventually our kids are going to do the same.

Long story short, how do I tell the man I love now that even though CARTER is a cute name, it’s just CANNOT be our babies name. Or do you ladies think I’m over reacting ? Advice ??

Update : I call him my first love because that’s what he is, we dated when I was a teenager, I’m about to be 25. There’s no feelings there, but to act like he was a regular ex would be downplaying our history, like I said we grew up together. Not to sound whoreish but I’ve had plenty of exes after him. It’s the fact that he was a staple in my life. That’s just... a fact. He was the first man I loved. To get jealous if your SO referred to his first love as what they were, A first love screams insecurity to me but hey, I’m the one asking for advice soo 🤷🏾‍♀️