Who was the young leader who fell in love with Queen Cleopatra and eventually had children with her and his death was said to be the cause of her suicide?

There wasn't any. It seems as if you have your history skewed. The big so-called love story was supposed to be between Mark Antony and Cleo, but Antony was by no means young when he met and was seduced by Cleopatra, he was in his forties. Yes, they did have children, but his death was by no means the cause of her suicide. The cause of Cleopatra's suicide was her pride. She offed herself to avoid being humiliated in Octavian's triumph in Rome.