Under Aged Kitten with Hobo Cat?

My kitten who is about 4-5 months old has started getting outside. She's SUPER fast so it's hard to catch her. We found her hanging out with a homeless cat and she seems really in love. She's been acting like one of those girls in romantic movies when they fall for a guy. So I found them snuggling outside together. We have 3 cats of which 2 go outside her and an older cat of ours who is also a guy. But we found that both of the guys don't get along well. But the homeless cat is WAAAAYY older than her so it's weird, right? But I was wondering if he could hurt her and if she could get pregnant? Thanks!