All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His Slave and Messenger.
You did not clarify in your question whether the partnership with your uncle has been terminated or not; therefore, our answer will be for both scenarios:
First, if the partnership is still ongoing and your uncle is taking money from the business without the permission of his partner, then such conduct is impermissible and the money he had taken in this manner is a debt on him. His share in the business remains intact.
Second, if the partnership had been terminated and your uncle had been given his due share, then he is not entitled to take anything from the business, not from its assets or from its profits. If he took money from the business in an unlawful manner, or because he knows that his partners will not object out of bashfulness, then he has committed an act of transgression and injustice. The Prophet said: "The property of a Muslim is not lawful (to his fellow Muslims) except if it is given willingly." [Ahmad]
Therefore, your uncle should be advised kindly and leniently. You may seek the help of people whom he respects and would listen to. If you advise him gently, then there is no blame on you for doing so.
However, we advise you to maintain the ties of kinship with your uncle by means of striving to avoid anything that may cause you to sever your relationship, especially since a paternal uncle has the same standing as a father. Abu Hurayrah reported that the Prophet said: "O ‘Umar, bear this in mind, the (paternal) uncle of a person is like his father." [Muslim]
Allaah knows best.