Although Derek turned 28 on May 17 and fellow 'Dancing With The Stars' professional Cheryl was 29 on May 3, the duo continued their celebrations with a pool party hosted by CIROC Vodka and attended by friends including Mark Ballas, Shoshana Bush, Ashley Roberts and Samuel Larson.
A source exclusively told BANG Showbiz: ''They had an amazing celebration. Cheryl cut the cake while Derek enjoyed the pool with friends but she got him with a lot of frosting to the face. They laughed and he made her lick it off.''
The delighted stars took to Twitter to enthuse about the party with Derek writing ''Thank you @ciroc for getting our summer started and throwing this belated bday party for Cheryl and I,'' and Cheryl adding ''Happy birthday to me and @derekhough ;) Thanks @ciroc (sic).''
It was recently revealed Derek and his sister, 'Rock Of Ages' actress Julianne, will choreograph and produce a brand new TV drama series set in the cut-throat world of international competitive ballroom dancing for US entertainment company Starz.
Carmi Zlotnik, Starz's managing director, said in a statement: ''Their experiences growing up in this highly competitive world are riveting and also shocking. There is much more to uncover than what we see on the dance floor.''
''Viewers are going to see a twisted, sexy, funny, dark and passionate side of the drama and politics in the world of ballroom dance that delves deeper than spray tans and sequins.''
The siblings' new project will focus an annual competition in the British seaside town of Blackpool.