He isn't
His connection to Val is that he is the husband of her mother's friend and a gym rat who will spend time with her there
Hmm guess I missed that connection, haven't seen any scene relating Gabi and Val's mom, guess I still have some more routes to follow. Still Navarro's concern for Val felt more personal, more like family than family friend. So I was thinking they were related somehow, either father or uncle. Then again he might be just a creep scouting for his next ex wife, looks like he has a type, latinas into sports... But on a serious note, regarding Navarro being Santi, I don't see it, Santi was a goofball, Navarro seems more of a serious type. He might have matured in his later years but that would be too much of a change. Take Emily for example, she is much more mature compared to her younger years but her playful personality still shows.
On a more important matter, this is still bugging me so much, who the hell stole Layla's hoodie???? Gotta remember to watch that whole scene frame by frame on my next playthrough to see if I can spot anything in the background.