The 45-year-old was re-admitted to Salisbury District Hospital last month – just weeks after he survived being poisoned by the nerve agent which killed his partner Dawn Sturgess, 44.
His sibling Matthew Rowley, 47, revealed Charlie had dialled 999 complaining that he was experiencing double vision.
Rowley said his brother is now “totally blind and has lost use of his limbs” after being diagnosed with meningitis.
He told Sky News: “I spoke to doctors and nurses and they say it doesn’t look good – he doesn’t have long left to live I fear.
“Charlie has lost hope because there is no sign of recovery. It’s not pretty – I spoke to him on Saturday and he said he can’t move his arms or legs.
“He is totally blind in a critical condition and has been diagnosed with meningitis. He has also lost use of all his limbs.
“His immune system was ruined by the Novichok and it made him susceptible to disease and illness. Sadly this is why he contracted meningitis.
“Charlie is in an intensive care unit and his speech has changed completely – the tone of his voice is almost incoherent, he sounds like a child, like a 10-year-old boy.
“I can’t get any sense out of him.”
A spokesman for Salisbury District Hospital said: “We can’t comment on individual cases. But, to reiterate what we have said previously, we are not currently treating anyone for nerve agent-related illnesses.”
Charlie and his partner fell ill on June 30 in Amesbury, Wiltshire, four months after the former Russian spy Sergei Skripal and his daughter, Yulia, were poisoned by Novichok eight miles away in Salisbury.
A murder investigation is underway into the death of Sturgess.
Wiltshire Police confirmed a car had been taken away from a police station on Tuesday as part of an ongoing probe.
“The public should not be alarmed by this. Those involved in the removal of the vehicle have the necessary training and expertise to carry out a variety of tasks, which includes the safe removal of vehicles,” the force said.
“The current advice from Public Health England is that the risk to the public remains low.”