Niagara Region police say the victims are a 76-year-old man and his 75-year-old wife from St. Donat, Que., and their 14-year-old grandson from Montreal.
A 55-year-old Niagara Falls man is facing charges of impaired driving.
Police say they were crossing the Niagara Parkway just after 10 p.m. when they were hit by a southbound Ford pickup truck.
The 76-year-old man died at the scene, his wife is in a Hamilton hospital with life-threatening injuries and the teen was airlifted to McMaster Hospital with serious but non-life threatening injuries.
Police say the driver of the pickup was not injured but faces seven charges including impaired driving causing death. He is being held in custody pending a bail hearing.
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