Her Billionaire Best Friend by Jo Grafford

It’s not easy for an undercover agent to be just friends with the woman he’d much rather be dating.

Titus Rand is sent to Anchorage by a top-secret organization to investigate Genesis & Sons. He goes undercover as the head of his own security firm to serve as a bodyguard — which makes his path cross again and again with Jolene Shore, a lovely nurse on their payroll. Unfortunately, his line of work leaves no time for dating.
His plan to keep his emotional distance from her falls apart when he’s asked to guard the newest ward of the Maddox clan, a long-lost brother who requires constant medical attention. Though he knows it’s best to keep his relationship with Nurse Jolene firmly in the friend category, it’s getting harder each day to ignore what his heart wants.