You assign a button to a family by giving it the same family number as other
members of that family. To assign a family number to a button, use the Family
pop-up menu in the Button Info dialog box. You can also assign a button to a
family in a script using the family property.
You can create up to 15 families on each card and up to 15 families on each
background.
When you add a button to a family (that is, give it a family setting of
anything except "none"), its Auto Hilite option is automatically turned on.
This article was adapted from the HyperCard 2.2 New Features stack.