How old is Ghost character in CoD?

Ghost in Call of Duty is in his mid-late twenties during the events of the main missions in the Modern Warfare series.

Simon “Ghost” Riley Returns to Call of Duty®: Mobile in a New Lucky Draw

Live the high life head-to-toe with the Bling Character Pack. Blind your enemies with a gold and diamond accented uniform and 2 different headgear

Call of Duty®: Ghosts - Bling Character Pack

Call of Duty®: Ghosts - Classic Ghost Pack on Steam

Simon 'ghost' Riley Jacket COD Task Force 141 Jacket

Ghost, Operator Skins in Modern Warfare 2 and Warzone 2

Simon “Ghost” Riley Returns to Call of Duty®: Mobile in a New Lucky Draw

Call of Duty: Modern Warfare Season 2 features Ghost, Rust, new battlepass - The Washington Post

Simon “Ghost” Riley (Reboot), Wiki

Who is Ghost? A history on Call of Duty's favorite Grim Reaper

Call of Duty: Warzone: 5 Most Famous Operators & Their Real Life Inspirations