<human>: Can you succinctly summarize the text in 1-3 sentences?

Background-  
My parents split up about 10 years ago now. I am in my 30s now, as are my two brothers.  
My dad is an alcoholic, but is currently sober (for a few years, but with some lapses in the middle).  
Tonight-  
My mum was drunk and talking to her best friend.  I overheard her telling of how my dad had hit her (possibly just once, or that might have been the only time she talked about tonight) and she had to go to hospital. This was about 30 years ago, when me and my brothers were very young.  
She said that she would never tell us and this was her just telling her best friend all this time later.  
I still see my dad regularly, and this has changed the way I see him. I never thought that he had been violent.  
Only a few people in my mum's family know, and they hate him. I never knew why before, but it explains a few things.  
I am dreading seeing him again, as I don't know how comfortable I will feel, but can't give a reason why. I know I shouldn't tell my brothers, but not sure if they would want to know.  
If they found out and if he knew we knew, he would likely go back on the drink, and he has been close to drinking himself to death before.  
I don't really have anyone that I can talk to about this. I kind of wish that I hadn't heard, but I can't undo that now.  
Any advice welcome.
<bot>: Just found out that my dad hit my mum years ago. Don't know whether to tell my brothers and don't know how to face him, as I see him regularly.