Let’s put this in perspective. You were 11. Your brother was 7. Neither one of you really knew what you were doing. If you were both 10 years older, it would be a whole different story. But you weren’t. You were kids.
What concerns me the most is that a 7-year old was this sexual. When kids that age are that explicit, I have to wonder how they learned what to do. Is he reenacting something that happened to him? Did someone show him movies he shouldn’t have been watching? Is he trying to make sense of something he saw?
Please stop trying to decide if these incidents were his fault or yours. If anyone is to blame, it’s whoever the older person was who was inappropriate with your brother. As you matured, you realized that something wasn’t right and you stopped it. Give yourself credit for that!
I do suggest that at some point you have a talk with your brother. My guess is tthat he is carrying around as much guilt and anger as you do. It would be a shame if you two are deprived of a relationship because of somebody else.
I wish you well.