"It is hard to believe that our little angel, our fighter from day one, our son 'Marlito' has unfortunately passed away and is no longer here with us," Marvin Jones wrote in an Instagram post Saturday night. "Marlo, the joy that you brought to us everyday, with that smile, and that energy was like heaven on Earth.
"You will always be in our hearts. We will always remember you."
Marlo was the youngest of five Jones children. Marvin Jones, playing in his eighth season in the league, frequently posts videos of his wife, Jazmyn, and their other children on social media and helps coach his eldest son in football during the NFL's off-season.
The Lions also showed support for Jones and his wife in a statement released Saturday.
"Earlier [Saturday], we were informed by Marvin and Jazmyn Jones about the sudden passing of their youngest son, Marlo," the team said in its statement. "The Detroit Lions fully support Marvin and Jazmyn during this extremely difficult time.
"Marvin and Jazmyn embody the true meaning of family, and the example they set has made them an inspiration to so many in our community. We thank everyone for the outpouring of support. On behalf of the Jones family, we ask that everyone respect the privacy of the matter at this time."
The Jones family attended the Lions' regular-season finale against the Green Bay Packers on Sunday at Ford Field. A moment of silence was held prior to the game in Marlo Jones' memory.
Marvin Jones, who is on injured reserve and didn't play in Sunday's game, was seen wiping away tears during the anthem, and he hugged multiple people on the sideline before exiting the field with his family.
In 13 games this season, Marvin Jones recorded 62 receptions for 779 yards and nine touchdowns.