To Gain and to Give: Hilchot Tzedakah, Day 18

Children who receive money from their parents as a means of support should not take ma’aser from this money. The parents are providing the money with the specific intent of supporting their children, and it is therefore understood that the parents are giving the children the money to use themselves.

אגרו"מ יו"ד ח"ב ס' קיב