You're "allowed" one, and maybe one asexual character and in some fandoms the fans police that you can have "one bisexual, all the rest of the queer characters are gay". Telling people what they can/should write and must not has become popular lately it seems. But yes, I don't care if they think it's unrealistic, because constantly seeing characters who didn't want children cave because the writers say so is worse to me, and ultimately a slap in the face to anyone who's never changed their mind. Let me write the alternatives :)