Help my fiancee's son wants to get pregnant?

my fiancee's son, Roman, is 13. hes been saying forever that hes not gay but just recently he started talking about partial sex change/reassignment surgery? he says he is not gay but he really wants to get pregnant... i think this is because hes adopted at the age of 9 and his mom cant get pregnant, so he feels bad... he even asked me if i knew any guys who he could ****!? i actually had a nightmare about it lol, hes only 13, it would be so gross! how do we talk him out of this? his mom alreaddy tried but he thinks shes being judgmental. i think if hes gay that's perfectly ok and he should just tell us rather than asking to get knocked up. has anyone seen this behavior in a straight male kid before???