Tender Beasts by Liselle Sambury

After her private school is rocked by a gruesome murder, a teen tries to find the real killer and clear her brother's name in this psychological thriller perfect for fans of The Taking of Jake Livingston and Ace of Spades.
Sunny Behre has four siblings, but only one is a murderer.

With the death of Sunny's mother, matriarch of the wealthy Behre family, Sunny's once picture-perfect life is thrown into turmoil. Her mother had groomed her to be the family's next leader, so Sunny is confused when the only instructions her mother leaves is a mysterious note: "Take care of Dom."

The problem is, her youngest brother, Dom, has always been a near-stranger to Sunny...and seemingly a dangerous one, if found guilty of his second-degree murder charge. Still, Sunny is determined to fulfill her mother's dying wish. But when a classmate is gruesomely murdered, and Sunny finds her brother with blood on his hands, her mother's simple request becomes a lot more complicated. Dom swears he's innocent, and although Sunny isn't sure she believes him, she takes it upon herself to look into the murder-made all the more urgent by the discovery of another body. And another.

As Sunny and Dom work together to track down the culprit, Sunny realizes her other siblings have their own dark secrets. Soon she may have to choose: preserve the family she's always loved or protect the brother she barely knows-and risk losing everything her mother worked so hard to build.