According to the Daily Mail it was Katy Perry who was not ready to settle down and start a family. And they seem pretty legitimate since they have the divorce paperwork:

The Daily Mail

Apparently Katy Perry was too caught up in being famous and being Katy Perry and she wasn’t ready to settle down, and she put her career ahead of family whereas Brand was ready to start a family. This is quite shocking, because we probably all expected that Brand would be the one to mess it all up.

By Nikky Raney

Because I'm Nikky Raney & you're not. Student, blogger & aspiring journalist as well as editor. I have already been a paid journalist and I have a lot of experience. Worked for political campaigns as well as at a television station. I am currently attending New England School of Communications in Bangor, Maine. I was Managing Editor and was one of the creators in 2006 of the largest student run newspaper in New England: The Tide, at Dover High School in Dover, New Hampshire. I was born June 7, 1990 in the Philippines. My personal site is The Future of Journalism - NikkyRaney.com You can follow me on twitter - http://twitter.com/nikkyraney