Why does everyone say "see if he is open to having other kids" when there's clearly another option: You can have kids with another man if he doesn't want to. Unless you identify as monogamous, i.e. you are only able to love one person at a time, then maybe you'll meet someone else down the road that you'll want to move in with and have kids with.
It's not wrong at all if you don't want to share your partner. But obviously, it does mean that this is not the partner for you.
One thing to note, if he's poly, he's far less likely cheat or leave you for another woman.
Gralson: my husband. Auto: my girlfriend.
Zoffee: Auto's husband. Cue: Zoffee's boyfriend. Bookie: Cue's wife.
"Love is not breathlessness, it is not excitement, it is not the promulgation of promises of eternal passion. That is just being "in love" which any of us can convince ourselves we are. Love itself is what is left over when being in love has burned away, and this is both an art and a fortunate accident. " -- Louis de Bernières