Talk to him again and talk this through. If you can have that conversation, which is hard, and adjust his equity to a reasonable amount, then your likely good of success goes up dramatically, partially because you fixed a real problem, but more importantly because you were able to do something hard.
At the minimum, their equity is under a vesting plan?
If they believe in this company and want to help it succeed, they can invest in it with a safe, which gets them equity rights and a strong incentive to help you succeed.
They take zero risk, they get no equity.
So I think the advice you would get from them is to apply and if you get an interview, make sure you can make a compelling case that you could still succeed without your Uncle being on board full-time.
It seems like their general guidance is "When in doubt apply".