The father of a missing Calgary boy says a large reward will be offered in relation to the disappearance of his son and the boy’s grandparents. An Amber Alert has been declared in Calgary for the missing trio. Five-year-old Nathan O’Brien has blond curly hair and blue eyes and was wearing peach-coloured shorts and a striped blue hoodie. Grandfather Alvin Liknes is 66 years old with grey-blond hair and was last seen wearing black sports shorts. He walks with a slight limp. 53-year-old Kathryn Liknes, has reddish-brown hair and green eyes and was last seen wearing pyjamas. The child’s mother went to the grandparents’ home in the southwest Calgary community of Parkhill at 10 a.m. Monday, but no one was there. Calgary police say evidence found at the residence, including marks on the ground, suggest the three may have been taken from the residence against their will. .Anyone with information can call the Calgary Police Service at 403-266-1234 or Crime Stoppers at 1-800-222-8477.