The “Forrest Gump” actor Gary Sinise’s late son, Mac Sinise, died in 2024 at 33 years old. He had been battling a rare form of cancer called Chordoma for over five years. The “Forrest Gump” actor Gary Sinise’s late son, Mac Sinise, died in 2024 at 33 years old. He had been battling a rare form of cancer called Chordoma for over five years.