According to E! News, the couple's rep confirmed the breakup in a statement:
"Hilary Duff and husband Mike Comrie have mutually decided to an amicable separation. They remain best friends and will continue to be in each other's lives. They are dedicated to loving and parenting their amazing son, and ask for privacy at this time."
What caused Hilary and Mike to separate?
According to a source, the couple "drifted apart over time," E! News reports, even though they attended couple's therapy.
A source close to Hilary told People.com: "There was no major incident--no big event between the two of them. They really did drift apart. They have put effort and thought into this decision for a long time. They tried couples therapy, but in the end, they realized at this time, they work better as friends. And they really are great friends."
The insider added that it was not "a rash decision," adding, "It's something [Hilary] thought through. She really does care about him and he really does care about her."
Hilary and Mike were marred in August 2010 and their son, Luca Cruz, was born in March 2012.
Hilary tweeted today: "Mike and I are sitting here,we are so appreciative for all of your kindness& well wishes. Not an easy day but we're getting thru it together"