Hilary Duff and soon-to-be ex-husband Mike Comrie have reunited to celebrate their only son Lucas' third birthday.

The 27-year old singer and actress, who just recently filed for divorce from the former Pittsburgh Penguin after they split in 2014, has put their issues and differences aside to happily celebrate their son's special day in Los Angeles.

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Hilary's pregnant older sister Haylie Duff, shared sweet photos from the party on her Instagram account, including one which showed Mike and her own husband, Matt Rossenburg, carrying Luca's cake. She captioned the photo, "Cutest Dad-to-be & Dad around!"

Hilary also took to her Instagram account to greet her son whom she addressed as her "love." She wrote, "3 years buddy! 3 beautiful years! You make every minute worth while (sic)! We cherish all your firsts and all that is to come. Happy 3^rd birthday my love #timeisflying #whatayear"

The "Youngers" star and Mike have always insisted that their breakup was amicable and in good terms. And while Hilary has hinted that the split will only be temporary, it seems like she's done with the relationship for good when she finally filed for divorce just last month, after Mike approached a woman and told her that he was going to pay her for sex.

A source close to Hilary revealed that she finally decided to end things between them because she realized Mike was not going to change his ways. He blew his chances and chose to live his life as if he were single.

TagsHilary Duff, Mike Comrie