If he truly loved Rick in every detail he would have never gotten with Lori in the first place regardless if he thought Rick was dead or not. Also he would have stepped away the minute he came back instead of literally sexually assaulting Lori. He is a grown ass man.
Watching TWD as an adult makes you realize Shane truly loved Rick in every little detail. But his obsession with Lori ended up being stronger than the brotherhood they had… and that's what destroyed them.