Looking for this "cheating thressome" type manga

I read this awhile back but I can't seem to remember the title. I remember it starts with the older brother doing it with his girl, and then his little brother was basically all like I can't take it anymore I gotta know what sex is like too, so he was basically implying he wants to do it with his older bro's girl. Of course his big bro was like no way, but then the girl was all like I don't mind in fact I'd love to, so the big bro lets it happen and it ends up in the threesome. At the end I think the girl was basically all like I'm lucky I got to try out brothers.

Please please if you actually know the title of this let me know. I know a lot of requests are kinda left unchecked on here. :(