Alex: when he sings to you. His voice is so beautiful. You love how caring and sweet he is, and the best way he expresses his affection is by writing you a song or singing to you.
Jack: when he makes dirty jokes. About 99% of Jack's jokes are totally disgusting but that turns you on.
Rian: when he plays drums. He's so strong and you love to watch him work.
Zack: when he works out. Just like he loves it when you work out. You think he looks really sexy when he's sweaty.