Police are desperately searching for a missing woman and her 10-year-old son, who are thought to be in Greater Manchester.
Kelly, 45, disappeared with Knox on July 28.
They went missing from their home in Patchway, a town in South Gloucestershire.
But Avon and Somerset police investigators think they might have travelled to Oldham and have urged anybody who spots them to call 999 immediately.
In a Twitter post, the force said: “Police and social services are concerned for Knox’s safety and welfare.”
Kelly is described as white, slim, around 5ft 2ins tall with brown hair and brown eyes.
If you see them, call 999 quoting the reference 5221171972.