Licking My Stepbrother's Asshole

I know this sounds crazy, but I'm freaking out right now...and don't know what to do. My boyfriend (who I really care a lot about, and don't want to lose him), he has been asking lately to.....lick his asshole! I have never done anything like this before, and I'm really nervous.
I don't want to ask any of my girlfriends, cause I don't want them to think I'm a freak or tell anyone at school. You know how gossipy 18 yr old girls can be. I know it's crazy but the only person I feel comfortable enough to talk about something like this, is my brother. We have always been super close and besides, he was the 1st person to know when I lost my virginity.
My brother could tell I was super nervous about something, especially after I double checked to make sure that mom and dad were down stairs watching TV...he knew something was up!
After a few moments of me beating around the bush....I finally just blurted it out. My boyfriend wants me to give him a rim job! Even my brother (who knows everything about me), was speechless for a second.
But then things got even more weird. Somehow I started to ask him if his girlfriend Shelly has ever licked his asshole? At first he was embarrassed to tell me, but after he could tell that I was actually serious...he confessed to me that he has let her tongue his butthole.
Then I did it.... I did something that I never thought I would ever do! I actually asked my brother if he would let me experiment on him, and let me lick his butthole!
Watch as my brother actually spreads his legs, and exposes his bare ass to me....allowing me to go down and lick my tongue all in the crevice of his open butthole.
Licking my brother's ass has gotten me wetter than I have ever been, and I started to notice my brother's dick growing larger right in front of me. Before I know it, I start stroking my brother's cock while rimming his hole. Then he flipped me over, for his turn to lick my butthole!
At this point we were both so horny we didn't even care that mom and dad were down stairs watching TV. My legs were spread for him, and he dipped his rock hard boner deep into my soaking wet open pussy. My boyfriend has never felt as hard as my brother's dick felt! It was throbbing as it slides in and out of me...
Then watch as I finish him off by tonguing his asshole, while stroking his pulsating cock till he exploded all in my hand and on his belly.
Even if I do ever give my boyfriend a rim job, I doubt it will ever top my 1st experience with my brother...