The Wild Dada Ducks is a fictional club. Certain books of mine are about the members of the Wild Dada Ducks. Also certain people who are not, (as yet), characters in books of mine seem to belong to the Wild Dada Ducks. These people may or may not be fictional. Such a person would be a Wild Dada Duck. I don't know of any actual feathered ducks belonging to the club, but I am hardly in a position to limit membership, (or readership), to humans.
If your brother-in-law makes a dada duck website, link it here.