Good question, Beth.

That certainly wasn't a brotherly love kiss, but I'm not quite sure it was a "kiss of death". Much like the situation with Mike killing Carlo, I believe Mike needed "proof" beyond doubt that Fredo was involved in the hit attempt. By Fredo admitting his role, he signed his own death warrant.

Yes, Mike realized Fredo was involved when Fredo "slipped" and said he had been to Cuba before with Johnny Ola, and Mike realized it, but IMO Mike was not prepared to kill Fredo at that time. I can't really back that up with fact... its just a gut feeling.