My sister forced me to restrain and pleasure her

A couple of days ago, my sister came to me with a strange request. She wanted me to restrain her while her friend was fucking her. At first, I was taken aback, but then I agreed. When her friend arrived, he immediately went to my sister and began to fuck her. However, my sister was not satisfied with just one person, and the guy had to join our brother. So, my sister and our friend could both enjoy their time in a threesome. I was not particularly excited about this situation, but I had to hold my sister and help her friend reach orgasm. The guy had a huge cock, which he managed to insert into my sister's shaved pussy. After a few minutes, he managed to bring my sister and his friend to an orgasm, and then they all left.