Deep regret, what can I do?

I regret so deeply that I used to physically abuse my little brother and sister when they were younger and I used to have to babysit them. I just used to get so sick of watching them and not being able to go out with my friends.
When they were alone in my presence, I would get easily irritated with them and holler and yell at them. I would make them do senseless chores like picking up lent from the carpet (hey that's what vacuums are for). But my most deep regret to this day, is that I struck my little brother in the face a couple of times. He was only about 3 at the time. I remember seeing the purplish marks from it on his face. I just hate myself for that. I can't believe he still loves me even though he's now about 23 and I'm 10 yrs older. Can I ever get over this guilt?