Need help deciding if this was Sa

Tw!!

I don't know if this is considered sa, but when I was 6 years old my mom was married to my step dad at the time and I had 3 step brothers and one step sister plus my biological brother. One of my step brothers was always really mean to me he was a teenager at the time. He used to do really mean stuff to me for example he would lock me in his bedroom during a storm when I power was out while I screamed and cried because I was terrified of the dark. But anyway that same step brother asked me and my step sister who was 4 or 5 at the time to come play with him and his friends in mine and her bedroom, I didn't think much of it considering I was 6 and I thought of him as my older brother, but when we all went in there he began touching me and his sister inappropriately and made us take off our clothes and him and his friends kept touching us as we were crying for them to stop and let us go his other friends were always guarding the door so we couldn't leave. They did that for 3 years. Is that considered Sa?