Am I wrong for havin' with my ex-boyfriend's cousin, even though neither I or his cousin likes him?

At the time my ex-boyfriend was my boyfriend, like any other relationship, we had our ups and downs. First time we broke up, his ex-girlfriend had his first son. I panicked, thinkin' he would get back with her, I lied. I lied and told him I was pregnant. Second time, this girl kept comin up, that he was suppose to be messin' with. He denied her, until she became pregnant by him. Third time, I got tired of sittin home waitin on him, so I decided to hit da Clubs, on a regular basis. He told me that I wasn't actin like a girlfriend. With da drama with him and between me and my mom, I decided to call our relationship off. Cause obivously there was somethin' else out there he wanted, reason he couldn't be or spend time with me. He flips da script on me, by sayin "I don't want you." Next couple days, up pops a picture on Facebook of him and his ex-girlfriend titled "The Family"(More to that). On her page is a picture of him proposin' to her, down on one knee with a ring. 6 weeks ped, he shows up at my house. We talked as friends, then he tells me that he isn't happy. They've been havin problems, she can't except his other baby. She asked him, If they were to break up who would he be with? I pretended not to hear him. Few weeks later, he ask me to take him back, I did, like a dummy. It seemed to have hit him that all I wanted was a little QT. Preparin' for our new start, he went off to drive trucks. Thinkin' when he came home he would wanna spend time with me. Instead he tells me he needs some "Me Time. WTF!! A week ped, I hit my usual "Pick Me Up", da Club. I run into his cousin. Been awhile since I had seen him. He would come over with my ex-boyfriend. I would ask my ex-boyfriend about his cousin, not knowin' they had a fallin out too. Boy, does his cousin talk. He told me about the other females and how my ex-boyfriend would give them money. How he was only messin' with me because he was bored. Babies he ain't claimin', and how my ex-boyfriend use to give details of our ual activities. His cousin once made a comment right in front of him, that he likes the way I'm built. Now, there an old rumor about his cousin, that he's "workin' with a monster". I'm single so I say "What da H***", let's find out if it's true. "IT"S TRUE!!" I'm wrong for doing this?? My friend say it will hurt my ex-boyfriend, will it? I don't think so.