He says he doesn’t want kids

My boyfriend is 20 I’m 21 we have talked about kids casually, no we’re not thinking about having them now or anytime soon. But he says he doesn’t want kids because they are expensive and he’s afraid he will be a bad parent, me on the other hand has always wanted kids I’m a preschool teacher right now and love working with them. Say we were to get married do you think I could change how he feels about having kids or is his mind set?