A 64-year-old woman was also in the home in Troy during the shooting Monday morning but was not harmed, police said.
Police responded to separate 911 calls saying shots had been fired in the home and a vehicle had struck a tree. Officers found one of the twins shot and killed in the basement and the other twin dead inside the vehicle from what police believe was a self-inflicted gunshot.
A family dog was found shot to death in the vehicle’s rear seat.
Their father was found wounded upstairs. In one of the 911 calls, a 62-year-old man said his 23-year-old son shot him, according to police.
Troy is about 24 miles (38 kilometers) north of Detroit.