A woman says the FBI interviewed her last month about her allegations that Dennis Hastert, the wrestling coach who would become speaker of the House, had a relationship with her brother while the brother was in high school.

Hastert – who during his term as House speaker from 1999 to 2007 stood second in line to the US presidency – was charged last week in a federal indictment that alleges he agreed to pay $3.5m to someone from the town where he taught and coached high school wrestling, so the person would stay quiet about “prior misconduct”.

Jolene Burdge told the Associated Press on Thursday that the FBI interviewed her in mid-May about Hastert. She said her brother told her before he died in 1995 that his first homosexual contact was with Hastert and that the abuse lasted through all of his high school years.

Burdge said he graduated from Yorkville high school in 1971 and that Hastert was his teacher and wrestling coach.

In an interview aired Friday on ABC’s Good Morning America, Burdge identified her brother as Stephen Reinbolt, and said Hastert had been a father figure to him at high school. But she also said she believed that relationship had caused irreparable harm.

“He damaged Steve, I think, more than any of us will ever know,” she told the morning show.

The AP could not independently verify her allegations.

A person familiar with the allegations in the indictment has told the Associated Press that the payments mentioned in the indictment were intended to conceal claims that the Illinois Republican sexually molested someone decades ago. The person spoke to the AP on the condition of anonymity because the investigation is ongoing.

Hastert has not been charged with sexual abuse. But Burdge’s story indicates there could be more victims beyond the “Individual A” named in the indictment.

Hastert did not respond to a message left on his cellphone early Friday. Emails and phone messages sent to his son, Ethan Hastert, were also not answered.

The FBI did not respond to a request for comment on Burdge’s allegations.

Reinboldt died in Los Angeles in 1995 at the age of 42. Burdge told ABC that he died of Aids.

Burdge said her brother told her about his past with Hastert in 1979, after she graduated high school, but never brought his story out into the open because he feared “nobody would believe him”.

The federal indictment, announced 28 May, accuses Hastert of evading bank regulations in withdrawing hundreds of thousands of dollars and lying to the FBI about the reason for the withdrawals. The document says Hastert agreed to pay a total of $3.5m to someone identified only as “Individual A” to “compensate for and conceal [Hastert’s] prior misconduct” against that person. But it does not go into any detail about the alleged misconduct.