Nepotism is the practice of showing favoritism towards relatives or friends, typically by giving them jobs or other opportunities. This practice can lead to unfair treatment and unequal opportunities for others who may be more qualified.
By becoming general secretary Stalin harnessed the unique oppertunity whereby he could appoint any member of the party to high power positions. He used this after winning the power struggle after Lenin's death to increase his own support and alienate any "factionalists". This could be described as political nepatism. However, he was appointed to this position due to the fact that, whilst being originally supported by Lenin himself, many members were averse to Trotsky's monopolising of the party and that Stalin seemed to not hold any threat.