Fry family

The Fry Family Tree

Minute Man Yancy Fry: Fought in the American Revolution; nothing else known. Enos and Mildred Yancy Fry, Sr. Yancy Fry, Jr. Philip J. Fry Philip J. Fry, II

Fry's time travel means that Yancy, Sr's paternal grandmother is his wife, Fry's mother. And not only did Fry become his own grandfather, he made his father his own grandfather as well. An infinite loop results: Fry is his own grandfather, great-great-grandfather, great-great-great-great-grandfather and so on. This abnormality is the reason Fry lacks the Delta Brainwave.

A much simpler alternative explanation is that Fry is not his own paternal grandfather, but maternal. This would solve the problem of accounting for how he obtained a Y-chromosome, and also why his mother's hair so resembles his own. The only evidence against this theory is that Fry himself seems to believe Enos and Mildred were his father's parents, but given his overall level of intelligence, it does not seem implausible that he could be wrong.

The paternity of Mom's kids was never revealed in the original run of the series, but in "Mother's Day" she describes Professor Farnsworth as "the only man I ever loved". However, in the film Bender's Game, it is revealed that Igner, Mom's youngest son, was fathered by Professor Farnsworth. It is also strongly implied that the other two may have been fathered by Dr. Ogden Wernstrom.