<human>: Can you provide a brief rundown of the text in within 3 sentences?

I've been friends with this guy for a few years and I've always found him attractive but never really had feelings for him, until now. He's been dating this girl for 4 months and ever since they started dating, I've started to develop a crush on him. I don't know if I have legit romantic feelings for him, or if it's just that another girl is in his life now and I'm being territorial? I think if they broke up these feelings would fade away. He hasn't had a girlfriend since we've been friends, until now, so this situation is quite new to me.

I don't know if I'd actually want to be in a relationship for him, I think it's weird that I only develop feelings for him once he has a girlfriend. That's why I'm thinking it's more of me just being territorial and protective of my friend. I don't feel anywhere near this strongly about my female friends when they get a new boyfriend though? So I don't know why? What's your guys thoughts?
<bot>: Ever since my guy friend got a girlfriend, I've started having a crush on him. I don't know if it's actual feelings, or if I'm just being territorial.