Throuple

About 3 months ago my boyfriend and I were sitting around watching a show and he had his phone in his hand, we watch some p*rn together once in a while and he handed me his phone with a video on it, I pressed play and it was a short clip, Seems like amateur stuff of two girls that it claims are twins sharing dude for a BJ and one jerks him off on the others face outside. I looked at him and he looked at me then he motioned to my sister who was sitting across the room.
My sister and I are twins, Not identical but very close, She is almost always with us everywhere we go and so I know they are about as close as two people not dating can be, I looked at him and squinted, He shrugged and chuckled a bit, I asked if that was something he wanted and he nodded yes, I thought for a minute and then decided to ask before I chickened out and said "Marcia...", She looked over and said "Ya?", I said "wanna suck Devin's dick?", She was like "WTF!!!! Macy...Jesus", I said "Come here, We will do it together".
She froze and stared at me so I just walked over, Took her hand, Walked her up to my BF and pushed down on her shoulders, She got on her knees, I got down beside her and he pulled down his shorts.
I know she has never sucked a dick before and he is my first but I think I must be pretty good at it since he cums every time, He only lasted about 5 mins and then grabbed her head but when he started cumming she gagged and pulled away, He held her hair so she couldn't go far and then stroked it with the other hand cumming on both our faces. About a week later he asked me to have her join us again, She did and then it became a once a week type thing. About a month ago I sat in a chair in the corner of the bedroom and masturbated while he fucked her hard and made her cum twice so no we all sleep in the same room when our parents are away and he stays over, We still go everywhere together and now we are just both dating him, We both hold his hand in public, We go on dates, Him and her go out when I work, Me and him go out when she works and so on so I guess we are a throuple.