Hynes is the center on the Marist High School football team, while Donegan is the quarterback. But the two seniors have played those positions on the same teams since they were fifth-graders.
"The best part is knowing you have your best friend, your brother behind you," Hynes said. "There's no other guy I would have wanted to go through these experiences with."
In the last seven seasons, the center-QB duo has played on squads that have earned a 60-9 record. They will try to improve that win-loss record during Saturday's IHSA Class 8A quarterfinals against Oswego.
"If we were strangers, we wouldn't have half those wins," Hynes said.
Hynes, 18, and Donegan, 17, met in first grade at St. Michael's School in Orland Park. Hynes said Donegan was always destined to be a quarterback, while he was thrown into the center position as a fifth-grader.
They won two league titles in sixth and eighth grade at St. Michael's before respective 7-2 and 8-1 records as Marist freshmen and sophomores.
They lost in the first round of the IHSA playoffs last year to finish 8-2, but have made a run to the Elite Eight this season, courtesy of last week's 21-7 victory over top-seeded Bolingbrook that upped them to 8-3.
"This team is just an unbelievably close group of guys," said sixth-year head coach Pat Dunne, who noted 11 of the 74 varsity players are St. Michael's alums. "Jack and Jack are very close, but they're extremely close with every guy on this team."
Donegan has thrown for 3,019 yards and 33 touchdowns on 351 attempts this season but has been sacked only five times. He credits his success to the trust in his offensive line, including Hynes.
"I always know he's going to do his job, and he's going to pick up his blitzes," said Donegan, who runs the offense almost exclusively from the shotgun formation. "It just gives me confidence."
Marist has been to the state championship game twice, in 1986 and 2009, and the RedHawks are three wins from their first IHSA title.
And while Hynes and Donegan haven't determined their college choices, it's certain they won't play football in pads together after this season. They plan to attend different schools.
"I try not to think about that," Donegan said. "Hopefully we have three games left together."
Eighth-seeded Marist hosts fourth-seeded Oswego at 7 p.m. Saturday at Marist High School, 4200 W. 115th St.