Francophone people often have prénoms composés, and I am told that the two hyphenated parts both compose one name and that I shouldn't address Jean-Jacques as Jean or Jacques, for example.
The question is whether this is also true between close people, like between family members. Does a mother always addresses her son as Jean-Jacques, not using shorter nicknames? If they do use nicknames, which part of prénoms composés are they often based on?