Philip Larkin was right.

I feel so sad for you morethan We are trying to support our darling DIL who has similar feelings about her sister. It's heartbreaking.

I feel sad for your sadness morethan you have enough to cope with without family relationships troubling you.
Let them sort it out and you concentrate on looking after the important things like you, your Dil and your GC, obviously your S himself but not his relationship with his sister,

My children were not raised the same. They have different birth order, one was first, one was last, 2 were middles. We were very young and poor when the first 2 were born. By time the last was born our business was very successful, a generation older, grandparents ourselves. All children have totally different childhoods and personalities to my view. Some do well with their life and others flounder, not to parenting at all. I do not like this be the verse.

morethan2 we only see things from our own viewpoint( understandably) when our families are growing up.The other thing is that sometimes adult children only remember the bad things ( a bit like remembering awful teachers etc)
Sounds as if you have been a good Mother, but your DH was away a lot so you had to deal with things.
Larkin really disliked his own parents ( maybe with good reason) and not that many, in reality ‘f—k you up’.
I can see why it made you sad though.?

No, you did not fail your son. It does not matter that he views his sister poorly, his relationship to her is his. That you couldn't shelter him from his sister's behaviour or the result of that behaviour on you, is normal. Dd was the problem, not you. He has a good relationship with you and his dad, in the end that's what matters.