The Michael J. Fox Foundation for Parkinson's Research is being sued by a woman who wants the organization to give back her deceased brother's generous donation.

Paul Aaron is believed to have given the foundation $250,000 after making it his sole beneficiary.

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According to The Blast, which obtained court documents, Aaron made the foundation the sole beneficiary of his Fidelity Investments account on Dec. 19, 2013. However, Jenny Malkin, Aaron's sister, says she should have been the beneficiary as his "only sibling and living immediate family member."

Aaron suffered from Parkinson's disease for more than 10 years.

In the lawsuit, Jenny argues that her brother "lacked the requisite mental capacity" to give the actor's foundation such a substantial amount of money and didn't "fully comprehend the nature and consequences" of his actions.

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Jenny argued that if her brother knew what he was doing, he wouldn't have been OK with "completely cutting off his sister, and other family members" from his finances.

The foundation has not responded to the lawsuit.