The West Australian construction baron died in 2014, aged 77, and there is a growing family feud over his $2.5 billion estate.

Two grandchildren, 19-year-old Esperance Stephen and her 16-year-old sister Alba, have launched a bid in the Supreme Court of Western Australia to secure their $90 million slice of the fortune held in trusts.

The sisters are not seeking more money, but instead argue the will does not make "adequate provisions" to ensure they receive their share.

Court documents show the teenagers are beneficiaries of two discretionary trusts, which entitle them to 5.6 per cent of the shares in the BGC Group.

Two of the building tycoon's children, Sam Buckeridge and Julian Ambrose, are the trustees and with their third brother Andrew have taken up the running of the BGC Group – one of Australia's largest private companies.

It is understood the sisters are unhappy because the current arrangement only entitles them to BGC shares, with no guarantee they could ever cash the shares in.

They are understood to be worried they would not receive company dividends either, which would be paid at the BGC board's discretion and distributed at the trustees' discretion.

One of Mr Buckeridge's daughters, Lise, has also launched action in the family dispute, which has grown to include 22 different parties and is set down for mediation in July.

The sisters live in Sydney's exclusive Vaucluse, where properties regularly go for more than $4 million, with their artist mother Rachel Buckeridge, who is reportedly also challenging the will.

The house was provided by their grandfather, the court heard last week.

An avid music fan, Esperance attended the local public school, Rose Bay Secondary College.

Her sister Alba appears to have taken after her mother's artistic passion, with an interest in Australian landscapes, indigenous recognition and environmentalism, according to her Facebook profile.

On the street filled with sheer white surfaces and sandstone arches, the Buckeridge homestead stands out as unique.

Immaculately groomed gardens give way to weeds at the three-storey abode that last sold for $3.7 million in 2010.

"Things fall apart," a banner unfurled from its second floor balcony reads.

Neighbours said there had been tension in the street over the encroaching plants along with noise complaints about late night gatherings and two dogs that stand guard at the front gate.

But few knew of the family's fortune or the Buckeridge sisters' battle to become two of Sydney's wealthiest teenagers.

"They keep to themselves." said one neighbour. "It's hard to know who actually sleeps there, there are lots of cars coming and going."

Their mother declined to comment when Fairfax Media approached her on Wednesday morning.

"I have to ask my lawyers and protect the privacy of my daughters," she said.

Some family members have also tried to sideline the only independent party involved in the dispute.

Andrew Teo has worked for Mr Buckeridge's company for more than 30 years, rising to the position of financial director and secretary, and was appointed as trustee to all five of the family's trusts.

He does not benefit from the estate, and "presumably it was for that purpose he was included as a trustee", WA Supreme Court Master Craig Sanderson told the court last week.

Yet two Buckeridge family members submitted that Mr Teo take little or no part in any mediation, using arguments the judge said were "seriously flawed".

Mr Teo, who is also non-executive chairman of the ASX-listed Medusa Mining, had to fight in court for permission to receive confidential legal advice and representation to administer the five trusts and to be reimbursed for those costs.