I've name changed as DH knows my usual name. I may just need to vent.
Trying keep it brief:
DH has struggled with a problem with alcohol since his late teens. Most severe problems were during a time when he was living back home with his parents house in his mid 20s, after having moved out previously. That was just before we met.
Both of us realise that alcoholism is not a thing that can be 'cured'. It has taken him 8 years of slow improvement with some tough times along the way, but it really seems that he now has control. I am so proud of him. He knows it's going to be a lifelong issue for him. It's early days.
We can talk openly about his problem between the two of us, but he has never talked about it with his siblings (all a little older than him and more outwardly 'successful' in life) even though they're quite close. It's years since his parents have have had any dealings with it.
And now we come to the problem.
His parents - particularly his mother - seem to view social events and family get togethers as an opportunity to drink. It's like a good time hasn't been had unless you've had a few too many. Conversations about outings or social occasions always conclude with her telling us she was plastered by the end of the evening, and what naughty fun it all was. It's always the very first thing she asks him on his birthday, or at xmas, or about an evening out: ''Did you have a few beers?'', and if he says no (as has always been the case these last 6 months, and quite often the case for some months before that) she seems disappointed for him. She will press him to drink when we visit. Recently, when she rang me to sort arrangements for a family meal at her house, she excitedly and pointedly told me how FIL had bought plenty of beer so DH could ''have some drinks with his brother''. I was heavily pregnant at the time and it's a 2 hour drive to theirs - so no way DH was going to drink. I told her he planned not to drink and there was quite an awkward silence 
(his brother has a 2 year old DD and tends not to drink at family occasions either now).
It gives me the rage and i don't understand it. She had him living with her at his worse fgs! A bottle of vodka a day + 8/10 cans of beer - and the many and varied horrible consequences for him and them. They literally dragged him to the GP more than once and pushed to have him registered as an alcoholic when he was 21. Has she just forgotten?!
It's pissing me off more and more as time goes on. DH loves his mum and i know would not hear a word against her. Therefore i've not tackled this with him. I don't know how to handle it. Should i even try? I need some wise words please.