When married movie actors/actresses kiss other people in movies

They probably married each other knowing that kissing on set would be a thing.

Part of the job. Not cheating at all.

Honestly, as a sort-of actress, I can tell you that acted-out kisses are pretty boring if anything.

In porn movies, kissing AND having sex, is part of the job. Just ask JohnOlinger1

It's a job. I don't think kissing is cheating regardless but not everyone feels that way.

part of the Job