My bf's bro watches us

Hi I'm Fiona and my confession is that my BF and me let his younger bro watch us when we fuck. I seen posts from people who say there sister has watched but this is wot happened to us.
we were doing it in my boyfriends bedroom (we r both 18 but it started last year when we were 17) and were right in the middle and he was making me crazy and i guess i was a bit loud. well we though his bro was out with his friends but i guess he came home and didn't hear him. he was 13 and he flinged the bedroom door opened and says WHAT R U2 DOIN??? My bf goes GET OUT but he just stood in the doorway. i suppose he could see my bf fucking me with my legs wide apart as he was ramming his dick in me. we thought he was gone cos the door slammed but when i looked over he was standing in the room with his pants down and his dick poking out of his underpants jerking off. then he comed all over the carpet. i couldn't believe it but we just kept going until my BF comed inside me. then his little says that he wanted to see us do it next time and if we said NO he d tell there mom so we agreed.
the next few times we were fucking his bro made sure he got to see it and then he got more braver and while we were doing it he got close to me and told me to suck his dick. well for sum reason it really turned me on more so i told him to come closer so i could take him in my mouth. i sucked on it for about 10 seconds when he comed in my mouth. afterwards my BF asked if i enjoyed it and i said i did so the next few times we did the same and i sucked off his little bro while my bf was fucking my pussy. now his little bro said he wants to fuck me to but that aint happening