Yeah, both parents beat the shit out of me until I started to win, and had to move out at ~ 16 or so.
I got married at ~ 20, started having kids myself at ~ 24, and, the first time my 4 year old was "being unreasonable", I FELT the rage well up and the urge to whack him.
It was SCARY...its like I had been TAUGHT how to raise a kid, and, ALMOST followed in my parent's footsteps...that was my FIRST reaction.
It was a sobering moment.
I cried, I thought I was a monster. Then, over time, I realized I had broken the cycle of abuse (parents, grandparents, all abusers).
I took heart at that.
I moved on.
My parents begged to see my kids, and, I refused. I didn't want them NEAR them.
Then, the KIDS wanted to see their grand parents. They wore me down, and, if supervised, I started to allow visits....and, then unsupervised as they seemed to be behaving.
There WERE a few cases where the kids told me some warning stories...but I had prepared them...so they knew the "tells".
Eventually, after some ups and downs...a new relationship was forged...and, it was actually enjoyable to visit with them, etc.
I finally (with my brother) asked WHY they used to beat us...and, they apologized, said it was how THEY were raised, and, were basically just taking out their frustrations on us.
About 10-15 years later, they changed their mind, and said they never beat us.
I think as they got older and older, they wanted their legacy with the grandkids, etc...to be "nice"....and rationalized away any conflicting memories.
They did not however ever do anything violent ever again...and my kids were fit middle aged men who could kick their geriatric butts anyway if they had.
But, all that aside, my Dad is still alive, but my Mom and all of my brothers are dead...but, I have a great relationship with my Dad still to this day.
I'm glad we mended the relationship, as its made my life and my family's life richer for it.
If he had NOT changed though, no way.
An old friend of mine, at age 22, unexpectedly found that his girlfriend was expecting their first child. He went through a phase of wondering if he would be a good father. It turned out that his own father was violent towards him. Well, violent on a good day and very violent on a drunken day.
His mother was always too timid (or scared) to intervene so by the time he was 17 he had left home. He never spoke too much about it. His main concern was that he was going to continue the cycle of violence and he was very scared that he might not be able to have any control over himself.
I started to tell him that he had already broken the cycle because he could see that it was a cycle and that because he was talking openly about it that he had control. He also never drank alcohol or did anything his father did, even down to not supporting the same football team.
It was like a light had gone off in his head. He was never going to confuse the anger he felt towards his father for the love he would feel towards his child. He broke down in tears. As he is my friend I join him. From that day on he invested his energy in his own family. He told his father that he could see his grandkids when he apologised. He waited until he was on his deathbed to do so.
Thirty years later my friend has three grown up children, all with first class degrees (and all atheists!) and spends his time playing with his ever increasing team of grandchildren and telling them how much he loves them. No point waiting until tomorrow to do so.