Dating my cousin?!

My cousin and i are a few months apart so we kind of grew up together shes my best friend shes like my sister to me. We had a good bond because we kept each other interested i was a weird dark guy n she was a Ms. Sunshine and out of a sudden we stopped contact because she moved far away and three years later they invited us for thanksgiving so thats when i saw her she turned dark aswell i couldn't recognize her at all and i was shocked because she got hotter and looked gorgeous so i started going to her home often and sleeping over and one day i told her my friend wanted to have sex with me and she told me to do it and that she wanted to do a threesome at first i was like no your my cousin but later i was like why not but later her and my friend said no so that night i slept over my cousin house and she layed right next to me and she said that she was bored so i gave her my phone n she searched up porn and we watched it and she whispered in my ear that she was so.wet n horny and in that second my aunt walked it and said to go to sleep so she left to her room and a few days later i told her that i wanted to fuck her n i asked her out she said yes and now we been dating for more than 4 month. Is it normal? She is the daughter of my mothers half sister