u mean H.H. Shaikh Jassim bin Hamad Al-Thani ?

he's the son of Shaikha Mozah, second wife of Amir, H.H. Shaikh Hamad bin Khalifa Al-Thani. once he was ppointed as Heir Apparent with the title of Crown Prince and style of His Highness 1996. renounced his rights in favour of his younger brother in 2003.