<human>: Hi, I'm an older sister to twins. I'm nineteen, they're fourteen (a boy and girl). My sister has had a couple boyfriend's before and I'd feel like proud of her, want to talk to her all about it and give advice, and in general I'd just think awehh that's adorable she has a bf, she's growing up. Now my brother has his first girlfriend and I just feel totally weird about it. I feel kind of like I'm "losing" him, and it just makes me territorial and I was kinda rude toward his gf the couples times I've met her. I love both of my siblings equally, I don't know why these feelings are so much stronger towards my brother than her. I worry almost that it could be some sort of strange attraction I have towards my brother? (I don't think I am in any way, but I don't know why else the opposite sex thing would make a difference) I don't want to be that older sibling who interrogates their sibling's SO, I also don't want to be controlling of him or tell him he's not allowed dating or anything. How am I supposed to deal with this and why do you think I feel that way?

Can you condense the text into three sentences or less?
<bot>: I have a little brother and sister, same age. I love them equally but am super overprotective of brother. I don't want him having a girlfriend, I don't know why.