The book I'm thinking of is one in a series. The first book in the series is about and girl who is a member of a softball/baseball team with several of her male friends. She ends up in multipartner situations with her friends from the team. One realizes he loves her and they get the HEA.

The second book, the one I'm really interested in, is about two men who are members of the baseball team and took part in the multipartner situation in the first book. They are friends and coworkers. One guy works in IT for the company. When he first moved there he was a skinny IT dork, but after purchasing a home with pool and going to the gym fills out nicely. They're friendship develops and grows. They have shared several female partners in the past. They become attracted to one another and IT guy initiates and things seem to be going well. IT guy even shares one of his regular female sex partners with his new lover. She was slightly older with red hair. IT guy is broody about his family situation in part of the book. Anyway, IT guy is taking things too casually when his male lover has become very emotionally involved. All the while they are hiding their new ****** relationship from their friends on the team.

Two importants facts: These are adults that meet for a friendly game of baseball in the park. (Not a pro-sports player book.) This is first full male on male sex for either partner.