He was rushed to a hospital in West Yorkshire earlier this week with multiple organ failure and placed in an induced coma.
Winehouse, who divorced Fielder-Civil in 2009, died on July 23, 2011 of accidental alcohol poisoning.
"Terrible news about Blake this morning. Remember Amy loved him," Mitch Winehouse, the late singer's dad, tweeted Friday. "Let’s pray for his recovery."
Winehouse’s sympathy is surprising, as he blames Fielder-Civil for introducing his daughter to crack and heroin.
Sarah Aspin, Fielder-Civil’s girlfriend and mother of his 15-month-old son, said he was showing signs of improvement late Friday. She found him unconscious at their home.
A recovering drug addict, Fielder-Civil had been released from jail recently after serving time for burglary.