The first time to see the in-laws, you can directly call each other as in-laws, if you know the other's age, you can call brothers, sisters, you can also call him according to the position name.
1, directly adDRESS each other as in-laws
If you know each other's age, you can call each other brothers and sisters, so it sounds more intimate, and everyone is about to become a family, so called is more appropriate.
3. Address the person by title