Schumacher, one of four people appointed by Hadid to take responsibility for her estate, has begun court proceedings to have the other three removed as executors – leaving him in control.
He began proceedings as he had "been left with no real choice in order to move matters along constructively."
However, the trio – Rana Hadid, Peter Palumbo and Brian Clarke – are fighting back. Rana Hadid, the late architect's niece, said her aunt "would have been devastated to learn what Schumacher is doing".
"Patrik Schumacher, a director of Zaha Hadid Architects, and an executor of the estate of the late Dame Zaha Hadid, has today issued a claim in the High Court in London against his three fellow executors," reads a joint statement from the trio.
"The claim seeks to remove these three as executors."
"Executors appointed personally by Zaha Hadid"
"These executors were appointed personally by Zaha Hadid because she trusted them to act in her best interests," continues the statement. "All three were known to Zaha for decades, one was a close family member, and the other two were very good friends."
The sum will be given to the Zaha Hadid Foundation, which Rana Hadid, Clarke and Palumbo are also trustees of, if they can not agree on how the money should be distributed. It is understood that Schumacher resigned from his position as a director of the foundation in June.
"Zaha would have been devastated to learn what Schumacher is doing"
The lawyer representing the three executors claims that Schumacher, who has led Zaha Hadid Architects since its founder's death, is trying to gain financially from the late architect's estate.
"The attempt to remove these three executors is totally unjustified and misconceived," said the lawyer.
"Unlike Mr Schumacher (who is seeking to gain financially from the estate), the three executors have no personal financial interest. They have at all times acted properly and in good faith with the desire to do their best for the estate given their friendship with Zaha Hadid."
Rana Hadid added: "We feel obliged to resist [Schumacher's] claims in order to defend her great name and legacy."
This is not the first time Zaha Hadid's friends and family have clashed with Schumacher. In 2016, following his controversial speech on social housing at the World Architecture Festival, Rana Hadid, Clarke and Palumbo said they "totally disagree" with his views.
"I have been left with no real choice"
Explaining his decision Schumacher stated that he wanted to move proceedings along in accordance to the Hadid's wishes.
"I applied to the High Court in London for an order to remove my co-executors Brian Clarke, Lord Peter Palumbo and Rana Hadid from the administration of Zaha Hadid’s estate, because regrettably I have been left with no real choice in order to move matters along constructively in accordance with the wishes of the late Zaha Hadid," said Schumacher in a statement.
"It will be for the court to decide the merit of the application," the statement continued.
Zaha Hadid Architects maintains that this is an issue for Schumacher and the other three executor to resolve.
"This is a matter relating solely to the executors of Zaha Hadid's estate," a spokesperson said.