Taryll, who is Micahel Jackson's nephew, is currently in the UK with his brother Taj and TJ, meaning he isn't able to celebrate with Adren in person.
Earlier today (18 February), the US singer uploaded a cute picture of his son - who is sporting a very Jackson 5-esque outfit - to his website.
Alongside it, he commented: "Happy 3rd Birthday to my baby Adren. You're growing too fast. (Only 3 and I'm already struggling smh.) Sorry I'm not there with you…Daddy misses and loves you SO much!" Aw!
3T's episode is yet to air on this year's series of The Big Reunion, however they will be taking to the stage at London's Hammersmith Apollo on Friday night with their co-stars for a one-off concert.
The brothers live in Los Angeles but have flown to the UK especially for rehearsals and the gig.
The Big Reunion 2014: Then and now
Copyright: Rex Features