Who did Tom Riddle Jr. (Voldy) Kill

[Steve Vander Ark]

No: HPFGUIDX 9840

As far as I can tell, there is no specific line which states that the 
three Riddles killed in 1944 were Tom/Volde's father and paternal 
grandparents. But I strongly feel that that's who they were. Here's 
why:

The three were "elderly Mr. and Mrs. Riddle...and their grown-up son 
Tom." That sounds like parent and grandparent to me. We know that in 
1944 Tom Riddle Jr. was just out of Hogwarts, since his time at the 
school coincided with the Chamber of Secrets being opened fifty years 
before 1992-3. In the stepbrother scenario, the younger person killed 
in the Riddle house in 1944, also inexplicably named Tom, would be 
about Tom Jr.'s age, but a bit younger. That makes him younger than 
17 or 18, hardly to be described as a "grown-up son."

I think it's pretty clear that on that fateful summer night in 1944, 
Tom Riddle Jr. left Hogwarts, traveled to Little Hangleton, where he 
was seen briefly by the gardener, a 28-year-old veteren of WWII named 
Frank Bryce. Later he confronted his father, Tom Sr., and his 
paternal grandparents, whose last name was Riddle but whose first 
names we do not know, in the drawing room of their mansion and did 
something to scare them silly before Avada Kedavra-ing them. He lined 
them up on the rug and set off to begin his quest for immortality.

I think it's pretty clear, but it is not stated specifically.

Steve Vander Ark
The Harry Potter Lexicon
http://www.i2k.com/~svderark/lexicon