Mad Man

Avi Mulvaney is many things: son, twin, owner of a fashion label, and a murderous psychopath. Together with his brother Asa, he makes one brutally efficient monster, ridding the world of predators who victimize the innocent — but their father has decided to test whether they do well apart.

Felix Navarro is a baby brother, fashionista, and vigilante in his own right. He isn't happy that his older brother married a Mulvaney, but the union has its perks, like a paid internship at Gemini — the cost being enduring Avi Mulvaney every day, which inevitably leads to thinking about him every night.

Avi is sent to help take down a dangerous crime ring and orders Felix to come along. Trapped together with only one bed, it's hard for Felix to hate Avi in the dark when he's whispering how Felix belongs to him. Felix belongs to no man — but Avi is determined to prove otherwise in one week.

Mad Man is book five in the Necessary Evils series, an intense enemies-to-lovers romance between two people neither of whom is entirely sane, with an HEA and no cliffhangers. Each book follows a different couple and can be read as a standalone.