Can also be related to daddy complex where they're filling a void that is missing, but instead looking for guys that are like their brother.
Guy: "Yeah, why do you play too?"
Girl: "Nah, but my older bro does. He's such a sweetheart.... I really miss him...."
Girl: "So do you also play Minecraft?"
Guy: "Let me guess your brother also played that?"
Girl: "Yeah, and he took me out to eat, and walked around with me at midnight, and told me how much he cared about me and would always be there for me. He wants nothing to do with me now though...."
Guy: "Do you have a brother complex or something? Why do you care if I do the same things as your brother?"
Boy 2: "Are you jealous?"
Boy 1: "NO! I just can't believe he left me."
Boy 2: "...Brother complex much"