A Sydney court has heard of the "secret marriage" of mining heiress Bianca Rinehart as a feud over who should manage a $5 billion family trust fund continues to play out in public.
John Hancock and Bianca Rinehart allege their mother Gina Rinehart acted "deceitfully" and with "gross dishonesty" in her dealings with the family trust fund.
The family matriarch and mining magnate, who is supported by her youngest daughter Ginia, has denied those claims, but agreed to bow out as trustee.
Every proposal so far for a replacement trustee - including Bianca Rinehart, Mr Hancock and independent trustees - has been knocked out of contention during lengthy NSW Supreme Court proceedings.
On Wednesday, the court heard that an entrepreneur proposed as a replacement trustee earlier this month, Sasha Serebryakov, was now Bianca Rinehart's husband.
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Ginia Rinehart's counsel Richard McHugh SC said he had only learned of their marriage "at the last minute" and that Mr Serebryakov should be ruled out as a potential trustee.
"This secret marriage that took place was a pretty good reason for objecting to it, on the grounds that (even) if he wasn't married to Bianca Rinehart, there are all sorts of problems associated with Rio Tinto," Mr McHugh said.
The court has previously heard claims that appointing anyone other than a "lineal descendant" to take the role would be a "kamikaze mission" because it would jeopardise a lucrative joint venture between the family business Hancock Prospecting (HPPL) and mining giant Rio Tinto.
Christopher Withers SC, representing Mr Hancock and Bianca Rinehart, said his clients were "actually acting in the best interests of the trust".
"It's not, obviously, in their interests to have their personal lives opened up ... but they're prepared to do it," he said.
But Judge Paul Brereton said he had to decline to appoint Mr Serebryakov.
"Having heard argument, I can't conceive of any circumstance in which the court would decline to appoint Bianca as trustee, yet be prepared to appoint her husband," he said.
The matter will return to court on December 3.
