My sister wants laiuti to do anal sex

my sister has a new boyfriend, and apparently has a fetish for asses. My half-sister had never fucked in the ass before now, he didn’t even try to put a dildo, so he was a bit worried. He told me the night we tried, but it was very painful. I already fucked some girls in the ass, so I offered to help her. He was really enthusiastic about my help. So we spent several days making practice….. first I did it with the fingers, I penetrated with hands, then we started using a butt plug, and finally I shoved my cock in her. How we did it gradually, when I fucked in the ass, it didn’t hurt. Had only a lot of pleasure.