Hello Quinnn: Thank you for bringing your concern here to PC. I see this is your first post. So... welcome to Psych Central. You mentioned you have an eating disorder. There's a forum, here on PC, dedicated to the subject of eating disorders. Here's a link:

https://forums.psychcentral.com/eating-disorders/

You asked if there is a chance your brother sexually abused you as a kid when you were too young to remember but old enough for it to have caused trauma... possibly resulting in your eating disorder. I'm not a mental health professional. So I can't offer you anything in the way of an authoritative response. From my lay-person's perspective, though, I would think that is certainly possible. Whether or not it is something that actually occurred, though, is another matter & one you would probably need to explore with the help of a psychologist or mental health therapist. Perhaps there will be other members, here on PC, who will have some personal experiences they can share.

Here's a link to an article, from Psych Central's archives, that discusses the link between trauma & eating disorders plus a second article that suggests memory isn't important to recover from trauma:

Is Unresolved Trauma Preventing a Full Eating Disorder Recovery?

Memory Isn't Important to Recover from Trauma

I hope you find PC to be of benefit.