What you are alleging is a conflict of interest. An attorney does not have to disclose a client list. You would have to make a motion to remove the attorney due to a conflict of interest.
If a conflict arises after representation has been undertaken, the lawyer ordinarily must withdraw from the representation.
In addition to conflicts with other current clients, a lawyer's duties of loyalty and independence may be materially limited by responsibilities to former clients.
Also, when lawyers representing different clients in the same matter or in substantially related matters are closely related by blood or marriage, there may be a significant risk that client confidences will be revealed and that the lawyer's family relationship will interfere with both loyalty and independent professional judgment.
So, if there is a conflict of interest, then you would make a motion to have the attorney be disqualified.
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