Many years ago, I heard the story of a man whose business partner did dirty. They were business partners for almost 5 years and the suddenly the business partner left with company's money. Even after several years, this man didn't recovered. He ended up sounding it as a warning to his kids never to go into business with anyone. The trust was destroyed and never recovered. This is just one of those sad stories.
On the other hand, there are many success stories of friends who went into business together and succeeded to together. If you have ever gone into business with a friend, what were your biggest concerns and how did work through it.
First-time experiences always have something to do with people's decisions, either positively or negatively. When one has a very bad partnership experience, it always gives them the belief that everyone might end up being the same, which is a very bad way of judging character.
Over to your question, I have not actually done any strong business partnerships with any friends or relatives; the only few that I have done were based on mutual agreement, which was just a simple business that doesn't actually require much trust.
If I am to actually enter into a business partnership with someone, be it family or whomever, it's always advisable to enter into a business partnership with someone with whom you have a mutual understanding, and at the same time, some form of legal agreement should be signed and sealed to enable each of them to hold on to their own part of the agreement. And when it comes to the monetary aspect, where trust is not guaranteed, one person should not be the only signatory to a business account, so that one person cannot go behind the other's back to withdraw the entire business's funds and make away with them.