<human>: So, I wanted opinions on this situation, since I was not 100% sure if this seemed scummy and a mutual friend felt it wasn't cool to do. Quick background, 22 F and I have been friends about 4 years, met in college and part of a small close group of friends. She and I were friendly and sometime last winter (can't recall when exactly) we hooked up at a party. Nothing came of it, I didn't wanna make the friendship weird and she never made a big deal of it. 

A few days ago she invited me and a few other friends to a family get together she had for her bro, who was leaving for the marines. I got put at a table with her, mutual friend and a few of her cousins. One cousin and I start talking, she's cute, clicks well personality-wise and she was flirty towards me and made the obvious "oh have a gf?" question that in my experience is testing the waters to see if she can make a move. 

I was going to ask her for her number, but mutual friend ended up talking to me alone and is like "hey that's 22 F's cousin and you two have been friends forever and she had a thing for you for a while, don't think its cool to ask out her cousin". I suppose I wanted second opinions of is this okay to do, should I do it, should I talk to my friend first before asking her cousin out?

Can you provide a brief overview of the text?
<bot>: Hooked up once with friend of 4 years months ago, met her cousin and clicked well, wrong to ask her out?