They were infatuated with each other when they wed in October 2010, but had only been together about a year at that point, and things went south fast.
People close to the couple say Katy and Russell were head over heels for each other, fascinated to be with a great person who was an extreme opposite.
The problems came when the honeymoon phase wore off.
After they got married, they fought constantly, often in front of people at clubs and shows. They're both stubborn and strong-willed, making things worse.
Their busy schedules didn't help, as they never spent long periods of time with each other. In the end, despite their attraction, they were "just too different."
Brand, who filed for divorce Friday, is more of a homebody than Katy, 27, who loves going out partying. Russell, 36, has been sober for years and didn't enjoy the scene.
He would often voice his desire to stay in or leave places early, asking her to come with him, which would trigger arguments. So it went. Not a long-term match.
At the end of the day, neither hates the other, there's no bad blood, and not even a hint of impropriety on either part. Just a mutual parting of ways.
Sad, but something a lot of people, famous or not, can relate to.