Only you should be the one who decides if it's a deal-breaker for you or not.
That was goin to be my answer as well.
Are there things that he would like to do before having kids? Maybe he wants them but now is just not the right time.
Depends on what u want.
"isn't sure " is not a definate no...but if children is important to you...you both need to be heading in the same direction for marriage. It's a decision you'll need to make on your own.
If you definitely want kids and your fiance isn't sure, don't get married until he figures it out. That's a massive issue and you don't want to go into a marriage with that hanging over your head. It could be a deal-breaker if you won't be happy without kids and he stays indecisive or decides he doesn't want them.
Do you want kids? If so and he doesn't, how will you feel about it in 10 years? During that time fr<x>ame, you are at your best for child rearing. Will you feel empty?
Yes, if that's the only thing you want from him :)
Nah it could change
Maybe it is.