we are good friends and we've been working together for 3 years now. when my other guy workmates go on vacation and come back, sometimes they greet me with a peck on the cheek too even if they were married. and there is no malice with it becoz i know it's a friendly welcome or greeting. and it's no different with this guy before. just now that he came back with his wife did he do that. the handshake is to mean them well becoz i'm really happy that he got married. i understand that he maybe he just doesn't want to upset his wife in some way.