Craig Wright, the Australian man who claimed to have invented bitcoin, is being sued for more than $10bn ($7.2bn) by the family of his former business partner.

The lawsuit, first reported by tech site Motherboard, alleges that Wright mined bitcoins together with Dave Kleiman, a programmer who died in 2013, after which time Wright “perpetrated a scheme” to “seize Dave’s bitcoins”. The plaintiff representing Dave Kleiman’s estate, Kleiman’s brother Ira, admits that the total amount of bitcoin in question is unknown – but says it is likely to be between 300,000 and 1.1m.

“It is unclear whether Craig, Dave, and/or both created bitcoin,” the lawsuit says. “It is undeniable, however, that Craig and Dave were involved in bitcoin from its inception, and that they both accumulated a vast wealth of bitcoins from 2009 through 2013.”

Filed in a Florida court two weeks ago, the suit alleges that, at the time of Kleiman’s death “no one in his family was aware of the extent of his involvement in creating bitcoin … recognising this, Craig perpetrated a scheme against Dave’s estate to seize Dave’s bitcoins and his rights to certain intellectual property associated with the bitcoin technology.”

The suit alleges that Wright later used forged documents to convince Kleiman’s family that the deceased coder had transferred full ownership of a company the two founded to Wright, W&K Info Defense Research. When Ira Kleiman questioned the documents, Wright promised that he would be “paid out of what was owed to Dave’s estate”, but the court filing says those payments never came.

Kleiman’s estate is seeking the value of the bitcoins Wright and Kleiman supposedly mined in the early days of the currency, as well as the intellectual property owned by W&K. The value of those assets, they estimate, “far exceed $5,118,266,427.50”.

Until 2015, Craig Wright was a largely unknown figure, even within the bitcoin community. But that year, he was investigated by the Australian tax authorities over his involvement with the currency, which led to speculation that he may be Satoshi Nakamoto, the pseudonymous creator of bitcoin.

In 2016, Wright went public, claiming he was indeed Nakamoto. But experts questioned the evidence he provided. He promised to provide further proof, but backed down days later, saying he was “sorry” and did “not have the courage”. Wright has remained a public figure in the bitcoin community, however, and never fully recanted his claim.