blech, my inlaws used to kiss on the lips and then my SIL tried to force my oldest to kiss her on the lips until the day she objected and I was standing there and told her “You don’t ever have to kiss anyone you don’t want to and if someone makes you do something you don’t feel comfortable doing, you come tell me or your father immediately. You don’t have to kiss anyone on the lips if you don’t feel comfortable doing so.” This gave my SIL the clear understanding that my child now had “mama’s permission” to decline kissing on the lips and she and I would have issues should she force my child to kiss her on the lips. I personally find it gross (unless kissing my DH or my kids when they are super small).