Sorry if this isn't allowed on this topic. I do not have alcohol issues myself but my DF and potentially my DM do.
I would definitely describe my DF as a functioning alcoholic although it has taken me years to accept that term. I still often second guess myself and wonder if I'm overreacting by labelling him that way.

When I still lived with them a lot of behaviours were excused or portrayed as normal and I never really questioned it or brushed off odd episodes of extreme drunkenness as "one offs" and often excused as work stress/health issue (DF had back surgery a few years ago but continued to work in a manual job) /insert other reason here. My DF would often say how sometimes you just need a drink to help you think through things both when talking about himself or DM having a drink/getting drunk.

I haven't realised how bad it is since moving out 6 years ago but my DBro has been keeping me in the loop recently, DF has sometimes gone 3-4 days drunk, he drinks in secret and there's bottles hidden all around the house and garden (DBro sent me a picture of an empty vodka bottle in a drawer of the spare room and said it wasn't there when he was looking for something the day before).
DM has been told by doctor to cut out any alcohol she might be having due to some test result yet she will still drink with DF and will brush off her horrendous hangovers and after effects as being caused by "xyz" rather than the alcohol she has been advised to stop consuming. DBro says her hangovers usually put her out of action for the day after with sickness/headaches and generally staying in bed - even if she has had a relatively small amount of alcohol.
She definitely does not drink as much as my DF but she shouldn't be drinking at all.

She tries to cover for my DF and is very tight lipped about it all.
we generally don't talk about the alcohol issue and they try to be very put together and proper when I visit with my DCs. Probably because they've been making notions about having them overnight/babysitting (not that me and DP would allow it) but again I never give a straight answer and avoid those subjects.

My DF has been known to drink drive in the past and call relatives and family members (including myself) when drunk either giving little monologues that don't actually have a point at the end/ trying to give unsolicited advice about any issues he knows they have or asking advice about his ideas/plans for potential business ventures which has recently come to the attention of my DGPs who have basically told them both off and told them to get help and maybe go to AA.
But they live hours away and can't really do anything else, they have been keeping tabs with my DBro about how my parents are doing and DM has asked my DBro to lie and fell out with him when he said he won't.

There's always a reason of what's causing them to drink it's usually general unhappiness cause by some outside influence. I think they both have MH issues and inferiority/insecurity complexes but I might be wrong.
I also realise they might be in complete denial about it when/if I bring it up.

There's more but I am very aware how long this post is already.

I am hoping for some insight and maybe advice on wether I should try and address it with them but I'm concerned it will just create a bigger rift between us and make it all very strained.

Has anyone dealt with something similar or perhaps was maybe on the other side of the problem?
They are only late 40s so potentially still have so much to look forward to including my wedding which I am at the moment seriously concerned about given the current situation.