Close relatives of Arlene Foster's former special adviser had 11 boilers in a botched green energy scheme in Northern Ireland, an inquiry chairman said.
Dr Andrew Crawford denied any involvement but said his brother James and two cousins who lived within 10 miles of him installed wood fuel burners to heat chicken houses used to supply meat to producer Moy Park.
The Renewable Heat Incentive (RHI) was established to encourage businesses to switch to more sustainable fuel sources but ended up running significantly over-budget.
Dr Crawford denies any efforts to delay the imposition of cost controls on the massively over-spending scheme in 2015 as civil servants wanted to take action and said the DUP wanted to "pin the blame" on him.
His evidence conflicts with that given by another former DUP special adviser to a public inquiry established to probe the matter.
Chairman and retired judge Sir Patrick Coghlin told Dr Crawford: "You have three family members, one brother and two cousins within a 10-mile radius who have installed 11 boilers."
The former senior DUP figure said he had purchased a "smallholding" which was completed in 2014.
This meant he owned fields adjoining a poultry unit established by his brother which was in the RHI scheme.
Dr Crawford said: "There was no financial link between myself and my brother in any way."
James Crawford was given a quotation from a boiler installer outlining the potential for his initial financial outlay to be paid off within three years using lucrative official subsidies, leaving 17 years of profit, a lawyer told the inquiry.
The judge asked: "They never said, 'Is it worthwhile me putting in these boilers in the scheme?'"
He wondered: "Would any of these close relations of yours with farms within a close geographical area never have said to you, 'I know you are working on this, it seems to be awfully profitable?'"
Dr Crawford said he had never discussed the finances.
He still associates with members of the DUP despite having left his job following revelations about his role in the RHI.
He said: "In my mind I was blamed unfairly."
He added: "I believe there was work going on behind the scenes to possibly pin the blame on me if possible."