My fiancé and I dated for several years before getting engaged, and both know each other's families well. I have always called his parents by their first name. When do I start calling them Mom and Dad? Katy, Waterbury, CT

No matter if you call them by first name, or Mr. and Mrs., it is generally best to continue to refer to them as you always have, until they suggest otherwise. It is also fine to simply ask them what they would prefer you call them, and see what the conversation brings from there. If you really want for you and your fiancé to refer to each other's parents as Mom and Dad, express this to him and ask him his opinion.