BEST FRIENDS OLDER BROTHER!!!!

Soo.. I’m pretty sure I want to hook up with my best friends older brother.. he just got out of jail a while back and he is just kind of sexy and I really want him in my guts.. like deep in my guts 😂😉😉 but my bsf doesn’t know I like him and idk if she would be happy if I did.. let alone have sex with him.. we don’t even talk much he just sees me when I stay the night.. he flirts with me I think.. he’s acts obnoxious when I come over so maybe he likes me to?... should I tell her how I feel about her brother or not ? Would it be wrong if I did have sex with him and not tell her??... btw were both 19 and he’s in like mid 20s I believe like we’re all adults he can make his own choices right?? Please help!?