What is the ruling on the deceased's cousin distributing his estate without court permission, and without enabling the heirs to review the deceased's will, knowing that the heirs are 9 sons, 13 daughters, and 3 wives, and one of the sons was a minor at the time of the estate distribution?

It is not a condition for the heirs to be adults for the estate to be divided. Rather, it is permissible to distribute it before that, while preserving the minor's share and allowing their guardian to dispose of it in a way that is most beneficial for them. If your cousin does not divide the estate according to Sharia (definition) or disposes of the minor's share in a way that does not serve their interest, the matter can be taken to the Sharia court. Your cousin must refrain from concealing or altering the will, for Allah the Almighty says: ﴿Then whoever alters it after hearing it, the sin thereof is only upon those who alter it. Indeed, Allah is All-Hearing, All-Knowing.﴾ And if you accuse him of that, you may refer the matter to the court for consideration. If the deceased left no heirs other than those mentioned, then the three wives receive one-eighth equally due to the presence of lineal descendants, and the remainder goes to the sons and daughters by ta'sib (agnatic inheritance), with the male receiving the equivalent of the share of two females.