(CNN) -- A former Microsoft executive and his son were aboard a turboprop airline that crashed Friday morning into two houses in East Haven, Connecticut, a family member told CNN. 

There has been "no official confirmation or positive identification" that Bill Henningsgaard and his son were on board, but there is no reason to believe that it was not the two of them, his brother, Blair Henningsgaard, said. 

Also feared dead in the crash were two children -- ages 1 and 13 -- in one house, East Haven Mayor Joseph Maturo Jr. said. The other house was unoccupied. 

National Transportation Safety Board investigators cannot confirm the number of people killed, saying there are reports of four to six people dead. 

Connecticut Gov. Dannel Malloy said there could be as many as five people killed in the crash, including up to three people on the plane. 

But Blair Henningsgaard said only his brother and his nephew were believed to be on the plane. 

Two bodies were seen inside the home but haven't been recovered because the home is unstable, East Haven Fire Chief Douglas Jackson said at a press conference Friday afternoon. 

Fire consumed both houses, preventing firefighters from searching for victims, Jackson said, and the basement in the home holding at least two victims was filled with water. 

Maturo said the children were in one house with their mother when the plane struck shortly before 11:30 a.m. The mother escaped, he said. 

"It's ... total devastation in the back of the home," Maturo said. 
One or both?
Also feared dead in the crash were two children -- ages 1 and 13 -- in one house, East Haven Mayor Joseph Maturo Jr. said. The other house was unoccupied. 