On the eve of their 50th wedding anniversary dinner, Uncles Mark and Robert, help their family come to terms with alcoholism, an issue threatening to destroy a beloved nephew.

Hi Mark, in loglines we usually omit character names:
On the eve of his gay uncle?s anniversary dinner, a troubled man must again battle with alcohol and the impact it continues to have on the family; all the while celebrating enduring love.
my two cents for you

Okay.....
Is this more of what you are wanting to see/read?

On the eve of his gay uncle?s anniversary dinner, Marcus must again battle with alcohol and the impact it continues to have on the family; all the while celebrating enduring love.

Still confused. "On the eve of their 50th wedding anniversary dinner" refers to who?

And who is the protagonist?