Naomi Watts and Liev Schreiber reunited for their son's 10th birthday.

The former Hollywood couple - who dated for 11 years before calling time on their relationship in September - put on a united front for the sake of their eldest child Alexander ''Sasha'' Pete, and the 'Ray Donovan' actor shared a family photo on his Instagram account of the stars helping their son cut his cake.

The actor, 49, captioned the heartwarming picture: ''Happy Birthday Big Boy! Finally hit the double digits! (sic)''

Naomi, 48, also showered love on her little ''man of the wild'' and wished him a happy birthday on Instagram alongside a picture of him standing on a fallen tree in Africa.

She said: ''Happy Birthday to this beautiful boy. Sasha is 10 today. Here he is in Africa, living his dream. His love and understanding of nature is everything. So lucky to be his mummy such a [gift] #inhiselement #manofthewild. (sic)''

Naomi is currently starring in the Netflix series 'Gypsy' and there have been reports that she's moved on from Liev with her co-star Billy Crudup who plays her on-screen husband.

The pair were spotted holding hands in Tribeca, New York, and were ''into each other'' as they enjoyed a casual lunch in a local cafe.

A fellow diner said at the time: ''Naomi Watts and Billy Crudup walked in holding hands. We didn't know they were a couple. Pretty cool seeing two big stars so into each other.

''[They] looked happy and were laughing a lot, then left again holding hands.''

A spokesperson for Naomi - who also has eight-year-old son Sammy with Liev - didn't respond when asked about the news, while Billy's representative simply said ''no comment''.

Just two months ago, the blonde beauty said she has high hopes that her and Liev can ''remain'' close moving forward.

Speaking about her former partner, she said: ''We have huge love and respect for one another and high hopes for it to remain that way going forward.

Meanwhile, Liev is reportedly dating Gerard Butler's ex Morgan Brown.