Who is Nick Palladino from The Deep End of the Ocean and what is their importance?

Nick Palladino is a successful man, whose first love was Beth Kerry. Beth, in fact, introduces Nick to his wife, Trisha. When Beth decides to marry Pat, the two go their separate ways. When Ben disappears, Nick tells Beth that he will do anything for her. Beth feels comfortable with Nick, and she seeks his companionship when she is at a very low point. She remembers their encounter fondly, but when she seeks to re-experience it, she realizes that she is not the only person he has had sex with outside of his marriage, and thus, she cannot be that special to him, since this is someting he seems to do regularly, even though he is satisfied in his marriage.