The Republican leader in the US House of Representatives reportedly paid his wife and daughter $500,000.
DeLay faces other sleaze allegations
The payments appear in Federal Election Commission statements and separate records in Tom DeLay's home state of Texas, says the New York Times.
While other Congress members employ relatives, these payments - via political committees - are reported to be particularly generous.
Mr DeLay's aides said the women had played a valuable role.
The Times says payments to his wife, Christine, and his daughter, Dani DeLay Ferro, were described in the disclosure forms as "fund-raising fees," "campaign management" or "payroll," with no further information about how they earned the money.
"Mrs DeLay provides big picture, long-term strategic guidance and helps with personnel decisions," Mr DeLay's Americans for a Republican Majority committee (Armpac) said in a statement.
"Ms Ferro is a skilled and experienced professional event planner who assists Armpac in arranging and organising individual events," it added.
Mrs Ferro has run a number of Mr DeLay's re-election campaigns for his House seat.
Democratic lawmakers and watchdog groups have also alleged that Mr DeLay violated House rules on travel.