Did I cause discouragement/depression?

This is a serious question. My brother used to have sex quite often. We started at young ages. For 7 years, I was away from home. When I came back home, I'd lost the desire for sex with him. The thought of it just felt awkward. I didn't give any notice that I'd lost interest despite seeing that he was still interested. He was dealing with other problems. I'm just curious if I could have contributed to them. Incest is a common practice, so this shouldn't be a shocking topic for anyone. I don't need any sarcasm.