Fry family

Description
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. Confusingly, this also means that Yancy, Sr., is married to his own grandmother. This abnormality is the reason Fry lacks the Delta Brain Wave.

The paternity of Mom's kids has never been revealed, but in Mother's Day she describes Professor Farnsworth as "the only man I ever loved". (There is also some resemblance between the Professor and Mom's children.) However, the same episode also claims that their relationship fell apart 70 years before the events of the show; Mom's children appear to be in their late thirties at most. Of course, Mom herself would have been too old to bear them naturally at that point, so one must assume either advanced 30th century obstetric technology or, perhaps, adoption. Therefore, their inclusion in the family tree is speculative, at best.

According to David Cohen, Mom's third son Ignar (the rather dumb one) is the illegitimate son of Prof. Farnsworth (which explains the character's hair). While it has been shown that Mom and the Prof. had a relationship across a few episodes, there was not enough time in the series before cancellation to reveal this particular result of that relationship. Though this is unconfirmed at the moment. source