Learning to share personal items at a young age fosters a sense of stewardship. The borrowing sister learns to care for things that aren't hers, while the lending sister learns the joy of altruism. The Unspoken Rules

Practically speaking, siblings who share enjoy a doubled wardrobe, a wider array of hobbies, and a shared library of books and media.

Every sister has that one item—a vintage heirloom or a splurge purchase—that is strictly off-limits, and that boundary is respected. Beyond the Physical

If you borrow it, you wash it, fold it, or refill it.

Many sibling rivalries are rooted in territory and ownership. By removing the "keep out" signs, sisters often find they have much less to fight about, leading to a more peaceful home environment.

Just because she doesn't mind sharing doesn't mean she wants things to disappear without a word.