We first meet Frank in book one. He is married to Kiera’s sister Libby. At the start of the story, Kiera is coming to America to live with her sister and Frank. Frank had inherited a big old house from his uncle. You later learn that his uncle committed suicide, after being haunted by a hell demon who fed on his misery.
Frank owns a security company that provides services to the Afterlight club and helps Kiera get a job there when she first moves to the US.
The little town that Frank and his wife Libby live in is called Evergreen Falls.
In one of the later books, you find out that Frank met Libby when she was at a concert who he was working as security. A fight broke out and he jumped in and saved her.