According to rahyafte (the missionaries and converts website)The Holy Messenger (pbuh) said about six and seven-year-old Imam Hassan and Imam Hussain (pbut),
“They are the masters of the youths of paradise.”
Although they were children – not young men – the Holy Prophet said that they were the masters of the youths of paradise. In other words, even though they were six and seven years old, they understood matters as well as young men. Their behaviour and manners were refined, and dignity radiated from them.
Imam Khamenei
source:hawzah
 are the masters of the youths of paradise,” the Prophet of Islam)
