Tiberius Kirk
From Memory Alpha, the free Star Trek reference
Tiberius Kirk was the father of George Kirk and the grandfather of George Samuel Kirk and James T. Kirk. His name would be the source of his grandson James Tiberius Kirk's middle name. (Star Trek)
In an alternate reality created by Nero, his given name was suggested by his daughter-in-law, Winona, as the first name of their son. Tiberius' son disagreed with the choice, and opted to have his son named after his father-in-law, James.
The establishment of "Tiberius Kirk" as James T. Kirk's grandfather originated in John M. Ford's TOS novel How Much for Just the Planet?, and only became canon with its inclusion in Star Trek.
