This question often comes up in the boating world as well, the sentiment is the same, a resounding no.
Another topic often related is whether to co-own a boat (RV) with a friend/family member and again the sentiment is usually no, there are always exceptional situations.
I would loan neither (boat, RV), there's just too many things to go wrong even on a good day. When something does go wrong, even if it was part that just plain reached end-of-life, I couldn't help but think if I was driving it may not have happened no matter what the issue.
My nephew, who I love dearly, started his career in financial advising. The first thing the business tells the new guys is to go after family and try to get their business. He approached me and I had been with Fidelity for years and liked my consultant, he has done well for us. I simply told him that money has a way of ruining family relationships and any losses that may result from his investing strategy would likely change our relationship forever; he totally understood.