I thought I did answer it (at least the one in the post). I was rather clear in saying: Don't do that. (... or so I thought?)
There were two different questions to hand:
"what would you design if you had funding?"
"what do you suggest I do with my cousin's offer?"
You answered the second by saying "don't do it" but the first question, and the one in the title of the post, you didn't answer at all, so I guess that Mratthew is technically correct in that respect.
I have to sort of disagree with your answer of "don't do it" though. I'm sure everyone would agree that you shouldn't waste the money, but that would hold true whether it came from family, or another funder. He doesn't seem to have experience, so he needs to be careful, he needs to do a lot of planning, but no-one goes in to any investment planning to fail.
Millionaires aren't millionaires because they just throw away their money, sure. But not all families are entirely unforgiving, or entirely capitalist in their intentions. The idea that a rich family member may be offering a small cash injection in order to get a family member on their way in a venture they enjoy isn't exactly an impossibility.
The important thing is to find out what is being offered, and the terms for the offer. How much is it? Is it a loan, gift, or investment? What does your cousin want in return? I don't know anything about the parties involved, so there's no basis for judgements. The sentiment to be careful with your family's money, makes sense. To say "don't do it because if you don't make any money then your family will be angry with you forever" is entirely speculative.