Theres a complicated situation with my cousin, his ex, me, and others.

So my cousin started dating this girl two years ago, they went through a lot. They've broken up several times, and it seems now for good. Ive asked both of them. So me and this girl are great friends and have always flirted, people always used to mistake us for dating. So i have feeling for her and i think she has them for me. They've both hooked up with others since they've "broken up." Ive also hooked up with a girl recently... well kinda thats also complicated, I've also got this other girl who i think is interested in me but also just seems like she's being friendly at times. Anyways do you think i should tell my cousins ex i have feeling four her at a party this weekend, or should i just try going for one of the single girls (i like my cousins ex the most btw), furthermore both the single girls kinda still like the other guys they broke up with... or a girl who's liked me supposedly for 3 years...theres no clear choice on who to try and have a relationship with. Who should i go with?