Historical sources give no explanation for their relationship, though there is some evidence which suggests that it was Shah Rukh's ancestry which had affected Timur's lack of favour, being the son of a concubine as opposed to a freeborn wife. Alternatively, there have been suggestions that Timur believed Shah Rukh did not possess the personal qualities required for ruling; the prince by this point had acquired a reputation for excessive modesty as well as personal piety. It might also have been this Islamic adherence and subsequent rejection of the laws of Genghis Khan, which had always been so strongly revered by Timur, that had resulted in the alienation of Shah Rukh from his father.