17-year-old refuses to give his gaming PC to his 13-year-old cousin after his aunt asked him to: 'He’d appreciate it more.'

If you haven't learned that stealing is wrong by the time you're in your 40s, you might not ever learn it.

A lot of parents feel conflicted about telling their children that they always have to share their toys. We're led to believe that encouraging sharing at a very young age will teach kids to be generous with others. That's probably correct, but it's not as applicable as you grow up. You shouldn't be expected to share all of your possession with anybody just because they ask! That would be a ridiculous thing to expect of people. Imagine a world where you're supposed to give a guy on the street your wallet just because he asked! That's obviously the most extreme example, but we don't expect people to share their possessions in most circumstances, even when they're objectively unvaluable.

Most people are taught to share when they're in preschool, and most people grow up to understand that you can't say yes to every borrowing request. It's totally up to you whether you let your sister borrow your clothes, and you're not a bad person for saying no. You might be afraid that she'll damage them, or you might have no concrete reason at all for saying no, and either are totally okay! I'm pretty willing to share a piece of gum with my friends, or my food with my roommates, but I don't go around lending my stuff to people I don't particularly know or trust.