In the past I've designated certain homebrew as "not ready" regardless of whether that was true, to keep visitors from cleaning me out.
But that was when I had only 2-3 homebrews in the house at any one time. These days I drink about 1 beer most days and make about 3.5 gallons a week. The math doesn't work out unless it is being given away or dumped when it starts to get old.
I get where the OP is coming from, but I think he's created a lot of it. "it is always up to me to serve beer" and "they expect me to bring homebrew or store bought beer."
I doubt that the family declared that he was the only person who can bring beer and if he doesn't bring something one time maybe they'll stop expecting it. As the "beer expert" they probably just think his choices will be better and need to be coaxed to purchase a bit of it themselves. Show interest in what they bring, mention some other good choices, and encourage them to do it again.
Basically, instead of being the Beer Guy, just be the Homebrew Guy, who supplements the beer others bring with homebrew if he's got any to share.