Wed in Thunder by Ashe Moon

All ice dragon alpha Marin needs is an omega. Cut off from the inheritance that funds his group of dragon firefighters, he must fool his family into believing he’ll produce an heir—and a contract marriage is his master plan to set things right. But when his search for a fake mate results in an unexpected family reunion, Marin finds himself tangled up with his estranged brother’s protective best friend, the deliciously adorable thunder dragon omega Shen.
Shen has always wished for a way he could help his friend heal from his traumatic upbringing, but this was not what he expected. In order to give Marin the time he needs to repair things with his younger brother, Shen agrees to pretend to be the alpha’s mate. A fake relationship is going to be his very first, but no problem—it’s all on paper, after all. But Shen is about to learn that when it comes to roguish ice dragons, nothing is ever so simple.