"Mrs. Bush was given the option of being discharged today, but has elected to remain at Houston Methodist Hospital one more evening to continue her recovery and to be closer to her husband," said family spokesperson Jim McGrath in a statement.
President Bush was struggling to breathe when he was admitted to the hospital Saturday. He remains in the ICU for observation, but he's breathing well on his own, with minimal supplemental oxygen.
Doctors hope the former President can be moved out of the ICU in the next day or two, McGrath said.
ORIGINAL REPORT: George H.W. and Barbara Bush hospitalized in Houston
Barbara Bush, 91, was admitted Wednesday and diagnosed with bronchitis after feeling fatigued and coughing for weeks. She could be released as early as Sunday, McGrath said.
PHOTOS: George H.W. Bush and Barbara Bush through the years
If you're viewing on our ABC13 news app, tap on the photo above to see more images.
Former President George W. Bush offered thanks on Instagram Thursday for messages "of love and support for Mother and Dad."
"Your prayers are working: 41 and Mom are doing much better today and fighting on," he said in his first public comments about their illnesses.
PHOTOS: The life and times of Barbara Bush
The Bushes were married Jan. 6, 1945, and have had the longest marriage of any presidential couple in American history. At the time of their wedding, he was a young naval aviator. She had been a student at Smith College.
After World War II, they moved to the Texas oil patch to seek their fortune and raise a family. It was there that George Bush began his political career, representing Houston for two terms in Congress in the late 1960s and early 1970s.
George Herbert Walker Bush, born June 12, 1924, in Milton, Massachusetts, also served as CIA director and Ronald Reagan's vice president.
RELATED STORIES: GEORGE AND BARBARA BUSH
George H.W. Bush and Barbara Bush celebrate 72 years of marriage
Former President George H.W. Bush marks 90th birthday today with skydive
PHOTOS: Former President George HW Bush through the years
If you're viewing on our ABC13 news app, tap on the photo above to see more images. null