Each brother is at the other's launch no matter what, supporting their parents as well as the other's wife and children.
This will be the fourth time Giffords, 40, has traveled to Kennedy Space Center for a launch. She attended her husband's liftoffs in 2006 and 2008 and her brother-in-law's in 2007. She was too busy campaigning last fall to make it to Kazakhstan.
Endeavour was supposed to fly in February, but late last year the launch was pushed into April because of delays with the preceding mission. That nixed any possibility of the Kellys crossing paths aboard the space station. Then Giffords was shot; had the flight remained on track for February, Kelly would have pulled out.
Scott, who served as space station commander, returned to Earth in March.
For Mark Kelly, the prospect of flying in space with his brother and best friend was enticing while it lasted. Who else might Kelly want to fly with in space?
"If it wasn't so dangerous, maybe my kids and my wife and my brother all at once," Kelly said. "But this flying in space stuff is a risky proposition. So I wouldn't let my kids do it, not at their current age."
After his wife was wounded, he took a monthlong leave from mission training, camping out at her hospital bedside in Tucson for two weeks until she was transferred to a rehab center in Houston, his home base. Her progress was so swift — and her rehabilitation schedule so intensive — that he resumed training in February at Johnson Space Center. That is what his wife would want, he explained.
Kelly, who is of Irish-Catholic descent, has publicly acknowledged his belief in the power of prayer in Giffords' remarkable recovery. She is Jewish; a rabbi married them in 2007.
"I hadn't been a big believer in faith until recently," Kelly said at the National Prayer Breakfast in Washington less than a month after the shooting. "I thought the world just spins and the clock just ticks and things happen for no particular reason."
Kelly was moved by all the angels, Bibles and prayers that appeared on the lawn outside his wife's hospital. One windless morning, as hundreds of candles burned at the makeshift memorial, he said he realized it was as sacred a spot as any church, temple or mosque: "A place with heaven itself as a ceiling."
From space, "you have an entirely different perspective of life on our planet," he said. "It's humbling to see the Earth as God created it in the context of God's vast universe."