Daniel McGrath Whalen is the son of Mary Suzanne McGrath and Martin Joseph Whalen (Sr.). He was born in 1966 in Illinois.

In 1992, he married Mary Elizabeth Telfer in Illinois. She was born in 1967 in Illinois.

Children of Daniel McGrath Whalen and Mary Elizabeth Telfer:

1. Jack McGrath Whalen was born in 1995 in Illinois.
2. Margaret Gale Whalen was born in 1996 in Illinois.