GOF - Riddle question

[freda18ca]

No: HPFGUIDX 130338

I am re-reading GOF and this time around noticed something that I can't explain. The 3 
Riddles are found dead - parents and a grown son, Tom. A teen-aged boy -pale with dark 
hair was seen by Frank Bryce, the gardener. What I want to know is -if Tom was killed, 
where did Voldemort come from? Is the teenager Tom? Explanations would be appreciated.

Freda