Going into business with friends or relatives is not a problem.
Just treat it like a business. When your cousin comes to work for you, you're under no different obligations as an employer than you would be if they weren't you cousin.
Similarly, business is something which people do for "profit". Whether than be salary, experience, shares, or literal profit - each person is there because they have something they want out of the business. As such, pretending that because they are family makes things different is idiotic.
The friend who says to his friends that he hired "Sorry, mate, it's not working out" is still a friend, but he's protecting his interest in the business. A friend that doesn't understand that is not a friend. And though there might be "favours" and shortcuts and digging people out of holes, those favours are as shortlived in the business world as they are in the personal world - and abuse of them by a friend means that they aren't a friend.
Speaking as someone who has in the past hired my own brother (and will do so again soon), and who my father found me work for occasionally with good friends of theirs, it's still "just business". They're not giving charity - if they were, they'd give charity as a friend.
If you go into business with a friend or relative, treat them like anyone else. Get a contract, get them to sign it, talk to them about what's happening, don't just assume they will always do what you want even when it's not in their interest. Don't rely on even a friend's goodwill to get you through.
You wouldn't take money from a friend just because they offered it. Equally you wouldn't run up a debt for your friend just because they "normally pay" or whatever. Talk to people. And get anything business-critical in writing.
Some guy you know coming to work for you for a few days can go wrong enough - don't think when you're talking multi-million dollar businesses and official share certificates that you don't need to make things official too.