Brother's Best Friend

A romance trope where the heroine's older brother's closest friend becomes her love interest, often sneaking around to hide their relationship from the brother who acts as a gatekeeper. The tension comes from betraying a loyalty oath while fighting an undeniable magnetic pull.

Readers love the forbidden thrill of a taboo crush getting a shot at legitimacy, plus the protective-beta-hero energy of someone who already knows her family and chooses her anyway. The sneaking and near-miss scenes deliver high-stakes sweetness.