• mother - she's usually/often cheery/in high spirits and she shares that and her humor with me even though i'm boring =p
• father - when he's not being a nasty, callous asshole, he's very sensitive in his own way. he often does what I really want even when I don't say it, and even when I say something opposite to what I want.
• youngest sister - she's very intuitive and entertaining. she's very her. when she was little she'd slide down the slide at the playground and then immediately pose, like "Ta daaaa!", it was adorable.
• best friend - his whimsical, creative silliness. nobody is silly exactly like he is, and it's perfect.

of course, I have to say that with each of these people what I actually love most about them isn't precisely the traits I mentioned but is simply their essences, which are simple yet totally unique and can't be put into words.