Mr Monroe =/= Santi... It is rather obvious that they are two separate people. This game would jump the shark if they were the same person which would also suddenly introduce incest into a game that the dev has said (probably because of Patreon) that there won't be any. Don't know why people keep insisting that Mr Monroe and Santi are the same person.Yeah. If you're on Gabi route you'll notice that there's picture on the wall. Gabi and Santi (probably). However it seams not all is functioning well in Gabi's marrige. Santi either cheats on Gabi (moron) or he's just workaholic. If i understood correctly he's having some high position in sports, tallent hunter or whatever. And Gabi simply isn't happy. Now if you played her route till the end of Episode 10 you'll notice that same pic on the wall is removed by Gabi, probably when she started the affair with MC, i presume right after the events in campus where MC and Gabi did you know what. I think that Gabi is going for a divorce.
As for Santi being theoreticaly dad of Layla and Lexi that were some of my thoughts cause if you're on L&L route we do see back of an older male character that almost resembles Santi. I wonder if our Santi comited poligamy. And if you're on Layla's route Adriana once mentioned that she gave birth to Lexi while she was 18. If you think about it it could be a reason why he refused to be a part of their lives and gave the role of dad to Andres.