This is from a post I wrote a while back:

According to Francis Fukayama in Origin of Political Order, Janissaries were initially forbidden from marriage or from having families. However, they were eventually able to lobby the Sultan to have this restriction lifted, as they were under Suleiman the Magnificent. Later on, they also successfully lobbied the Sultans to allow their sons to follow them into service. Under Murad IV, the original recruitment system for the Janissaries was abolished and the corps became largely hereditary. The Janissaries would eventually go on to became less of a warrior class and more of a commercial/rent-seeking class, continuously lobbying the government for their own material interest. In essence, their loyalty to their families ended up overriding their loyalty to the state. Something very similar happened with the Mamluks, basically none of the Middle-Eastern states were very good at dealing with the formation of patrimonial classes of rent-seekers.