You could show him the recommended gov guideline which can be found online then compare it to the levels of alcohol he consumes. This can be a way to invite him to explore his drinking problem.
You could ask why he drinks, and when he responds like ” to chill out” that implies an issue as it indicates one needs a drink to relax etc.
It’s really difficult for you Broaching a discussion like this because often people in addiction might be in denial, fearful and or somewhat unsure themselves, typically if they’ve never had any kind of support previously.
It’s hard to know what to suggest as you’ve not really said much about the situation.
Try Al Anon for support as well, they help families affected by substance misuse.
On the homepage is lots of info. Plus your local Drug and Alcohol service near you. GP and AA meetings. Plenty of support about.
Best wishes