My sister’s boyfriend, Cas, left his bike on my parent’s farm, and one day one of the cousins saw it just laying around and asked my dad if he could have it. He thought it was one of the worthless abandoned bikes we used to have and said ‘sure’.
Now Cas would like his bike back but feels the improvements my cousin made are worth more than the bike, specially because it was a pretty old bike. And they’re friends too, he doesn’t have the heart to demand it back.
Declare that you’re going to cut the bike in two and give each half. Whichever says “No! Give it to the other person” gets to keep the bike.
No? Heh, okay. How would the two of them feel about your cousin keeping the bike but giving Cas some nominal amount as reimbursement for the base he built upon? That seems only fair, they both get something out of it and with an agreement there’s no hard feelings left over.
Also… if there’s a big wealth discrepancy between the boyfriend and the cousin, that should be taken into account, too. If the cousin is well-off, and the b/f works at a gas station, the right thing to do is give the bike back.
I say it’s the cousin’s bike now. If sister’s boyfriend feels he was unjustly deprived of his property, the person he should take it up with is the person who gave it to the cousin, i.e. your dad. Since it doesn’t sound like it was particularly valuable, I’d advice him just to let it go and get a new bike.
Dude - they’re friends. Just put them together and say, “Hey - he wants his bike back. But you took it and fixed it up. Maybe you should just pay him $50 and then you can keep the bike and he’ll get a new one.” (Obviously it doesn’t have to be $50 — it could be $100 — it could be $10. Just pick a number that you think is fair). That’s how I would handle it with my buddies. That way it’s not something unspoken and unresolved. Speak it and resolve it.