Five record companies, represented by the Recording Industry Association of America, filed a lawsuit in federal court in White Plains, N.Y., on Wednesday against Santangelo's son and daughter.
The lawsuit against the mother is still pending and is separate from the one against her children, the Santangelos' attorney, Jordan Glass, told CBSNews.com.
It said Michelle Santangelo, 20, has acknowledged downloading songs on the family computer and that her brother, Robert, 16, had been implicated in statements his best friend made. It accuses the two of downloading and distributing more than 1,000 songs, including "Pretty Fly (for a White Guy)" by the Offspring, "MMMBop" by Hanson and "Beat It" by Michael Jackson.
"In short, each of the defendants participated in the substantial violations of plaintiffs' copyrights at issue and then concealed their involvement, standing idly by as Patricia Santangelo repeatedly protested their innocence and chastised plaintiffs for filing allegedly frivolous litigation," the complaint said.
Glass disputed the recording industry's allegations and said he was at Michelle Santangelo's deposition and does not recall her "admitting or acknowledging downloading."
Patricia Santangelo, whom a federal judge called "an Internet illiterate parent," drew attention last year when she denied downloading songs and refused to settle with the recording industry, which she said demanded $7,500 to keep her name out of a lawsuit for illegally downloading music.
Santangelo said on CBS News' The Early Show last December that she keeps a very close eye on her children's Internet activities. She said she has never downloaded music and wouldn't even know how to, and thinks one of her kid's friends may have been downloading music from her home computer.
"I know nothing about them downloading music or trading files," she told co-anchor Harry Smith.
Defenders of Internet freedom helped pay for her attorney. She proclaimed her innocence on TV. But the question remained whether her children had done it. Santangelo said she had no knowledge of them downloading and, if they did, the blame lay with computer programs, not with her or the children.
The industry is requesting an injunction, unspecified damages for each download and court costs.
The record companies have sued thousands of people, including many minors, for allegedly pirating music through file-sharing computer networks, most of which have been forced out of business.
"It's a way that is actually proven very effective," Cary Sherman, president of the Recording Industry Association of America, also said on The Early Show in December. "I understand Ms. Santangelo looks at this from her unique perspective as a defendant. She has to understand that there are tens of thousands of other people who are engaging in this activity, and they are decimating the music industry collectively.
"Half the songwriters in Nashville don't have their jobs from just five years ago. Their royalties are down. Artists can't get signed to label rosters anymore."
"These lawsuits are designed to tell people, educate them that this activity is illegal, you can be identified and there are consequences when caught," Sherman said.