Fugitive Michael Lynn has fathered two children with his wife Brid despite being locked up in an overcrowded Brazilian jail.
The revelation emerged in a submission to Brazil's Supreme Court, as the former solicitor sought once again to delay his extradition to Ireland.
Lynn faces 33 charges relating to an alleged €80m mortgage fraud, after failing to show up at the High Court in Dublin in 2007.
The couple fled to Brazil, where his wife Brid gave birth to their first two children in August 2011 and November 2013, according to court documents.
But Lynn has been imprisoned since August 2013 when Brazilian federal police, acting on behalf of Interpol, arrested him near Recife, north-east Brazil.
Since then, the disgraced businessman has been held in the Cotel prison alongside murderers and rapists.
His wife, however, has since given birth to two more children, in February 2015 and October 2016, court papers said.
It is not clear how these were conceived, but Lynn's submission, in arguing he should be allowed to remain, states that he is the father. The couple's children are now aged five, three, two, and seven months.
Last week, Judge Marco Aurélio requested representations from the Irish Government on the submission from Lynn. Famously, Great Train Robber Ronnie Biggs avoided extradition from Brazil to the UK after fathering a child.
But it is understood that Brazil's 1980 Foreigners' Act now does not prevent the expulsion of a foreign national from the country, if the child was born after the alleged crime was committed. The Irish Government's lawyers are said to be confident the latest in a long line of petitions by Lynn will not eventually stop his extradition.
Judge Aurélio first ruled the former solicitor should be extradited in December 2014. But three times since, his lawyers have sought to "request clarification" of the judgment.
It is a decade since he failed to appear at Dublin's High Court and nearly four years since he was arrested in his beach villa near the city of Recife. At the time he fled, he had debts of €80m and his company was said to have 148 properties, 154 bank accounts and assets worth more than €50m.
In Brazil, he lived openly in a villa near a beach while teaching English to the locals, and joined a country club.
He would also visit the nearby office of Quantum Consulting and Ventures, a €500,000 company he had registered in yet another shot at the property market.
But his comfortable new life came to an end in August 2013 when Brazilian federal police, acting on behalf of Interpol, swooped at a shopping centre near his home.
His request for bail was denied and he was told to "shut up" by another judge for talking back during an extradition hearing.
Judge Aurélio also turned down a long-running campaign by the fugitive to be transferred to a private hospital after he said he may have tuberculosis.
While there is no extradition treaty between the two countries, a bilateral agreement was struck meaning Lynn can be extradited.