During the earliest period of the rise of Muscovy, a class of boyars formed in Moscow (see chapter 43), who were true to the knyazes. The old tradition gave the boyars and free servants the right to leave their lord if they were dissatisfied. The nobler servants, boyars, also had the right to participate in the knyaz's duma (council) and discuss all questions regarding the state politics and administration. In the XIV century, boyars rarely excercised the right to leave the knyazes, since Muscovy was the best place for the aristocrats. On the contrary, they came from other principalities and asked the grand knyaz for the permission to become his servants. They had their share in the gains of Muscovy and did their best to assist the strengthening principality. The grand knyazes also cherished their servants. Dimitri Donskoy told his chidren before his death: "Love the boyars, honor them and do nothing without the council's approval."
The most notable among the boyars were the families of Fyodor Koshka (Romanovs and Sheremetevs), Byakont (Pleshcheyevs), Murza-Chet (Saburovs, Godunovs, etc.), the families of Golovins, Morozovs, Velyaminovs and many others. Since XV century, many knyazes from northern Rus and Lithuania became boyars in Moscow. They joined Muscovy with their lands and the knyaz left these lands to them as patrimonies. Some Lithuanian knyazes who had to leave their lands, were granted new patrimonies. So, the boyars had to serve the knyazes and received the lands as payment. These knyazes became actually simple servants of the grand knyazes, but because of their noble origin and belonged to the descendants of Gediminas or Ryurik they considered themselves higher than all other boyars. They still remembered who of them belonged to a more noble family ("older") and who was less noble ("younger"). They measured their nobility by their position within their clans, or otechestvo.
However, for the old boyars these knyazes were newcomers and the boyars wouldn't lose their priority. They had their own families and they had their own otchestvo. Their positions in their families were taken into account when knyaz appointed them to new positions. The boyars only agreed to occupy a vacant position when they were sure that they will not be subjects to "younger" boyars. This tradition was called mestnichestvo.
So, in the XV century the aristocracy gained the new form and the former knyazes and their descendants became the upper layer of this new aristocracy. They became known as knyazhata. Since their forefathers were noble independent knyazes and not simple servants of the grand knyaz, they ruled in their patrimonies as if they were the single lords of these lands, like in the older times, and their desire to become the co-rulers of the grand knyaz, of course, worried the grand knyaz. However, the grand knyaz could not raise or lower the otechestvo of the knyazes and could not make them "less noble" than they were. So, the peace between the grand knyazes and the boyars was broken. Neither Ivan III nor Vasily III recognized the ambitions of the knyazhata. Both grand knyazes deprived the knyazhata or their patrimonies or prohibited to sell them to prevent the loss of the lands belonging to Muscovy. Knyazhata were not allowed to participate in the grand knyaz's duma (council). If knyazhata asked the grand knyaz to restore their rights, they were sent to exile, to monastery or even executed. Those who attempted to secede and join their lands to Lithuania (since there was no other country to escape to), were accused of treason. So, the grand knyazes deprived their noblest servants of the ancient rights: the right to participate in duma and the right to leave their lord. The knyazhata did not understand that the new times had come and that in the new state the secession was a real treason. So, knyazhata finally became the enemies of the grand knyaz.