Davis fostered Whitney as she was a teenager, when she joined the music world. She died three years back in her hotel room at the age of 48.
Her 21-year-old daughter is on life support since last week, after being found unconscious in a bathtub at her home in Georgia. A cousin of Bobby tweeted that chances of her survival seemed less.
"It's very painful and heartbreaking to see the family go through such pain again," Davis said, comparing Whitney and her only child's state.