Male Amnesia Romance part of three part series where son catches dad in affair with his girl bestfriend

[Christina]

Son loses memory after catching dad in affair with his girl best friend. Part of a three part series where the son’s best friend gets pregnant and the wife forgives the husband for the affair.

Love triangle book where the son I think is getting engaged but the other women shows up and tries to win him back.

[Kris]

Christina, around what year did you read this book series?

What caused the son's amnesia?

Main characters' jobs?
Story's time period and location/ country?