Michael Jackson's son Prince Michael celebrated his 18th birthday on Friday (13Feb15) by thanking his late father in a heartfelt letter.

The teenager posted his thoughts online on Thursday night (12Feb15), also offering up his gratitude to his grandmother and cousin T.J. Jackson, who have served as his joint guardians since the King of Pop's death in 2009.

He wrote, "Before I turn 18 tomorrow I really want to thank a few (people) and first is obviously my dad. He was and is an incredible human being... he gave me an incredible opportunity to make something of myself."

Turning to T.J. the 18 year old added, "He has made so many sacrifices to help me along and he's been there when I needed him and help shape who I am (sic)."

Prince Michael concluded his birthday eve letter by calling his grandmother Katherine "a strong woman... who has been through so much".

He added, "She’s an inspiration to keep going no matter what."