Exactly one month after filing for divorce, Hilary Duff included her estranged husband Mike Comrie in a sweet birthday Flipagram message for their son Luca -- see it here. Credit: Steve Granitz/WireImage.com

All the love for little Luca! Exactly one month after filing for divorce, Hilary Duff included her estranged husband Mike Comrie in a sweet Flipagram message for their son, Luca, on his third birthday, Mar. 20.

"3 years buddy! 3 beautiful years!" Duff, 27, wrote alongside the snaps of her little boy. "You make every minute worth while!"

The Younger actress, who filed her papers Feb. 20, amicably included the former NHL pro, 34, in multiple photos and in her message. "We cherish all your firsts and all that is to come," Duff wrote. "Happy 3rd birthday my love #timesflying #whatayear."

Indeed, she and Comrie have remained on good terms after their January 2014 split announcement, which Duff discussed at great length in the April 2015 issue of Cosmopolitan. "Mike and I were very in love when we met," the former Disney Channel star reflected. "We both really wanted to get married... Maybe it wasn't [the best decision], but we spent the majority of our time together really happy."

In January 2014, the seemingly happy pair announced their separation in a joint statement.

Duff waited for a year before filing the documents on Feb. 20, one day after Comrie's raucous night out was reported by a paper. A source close to the actress confirmed the report to Us Weekly, saying she "finally realized Mike wasn't going to change."

Regardless, the star told Cosmo she was ready for a fresh start. "I don't know if people are meant to be together forever. Things happen over a long relationship that you can't always fight," she shared. "I just always want to fight for happiness."