Joseph Robinson Jr., 50, of Tenafly, and 46-year-old Leland Robinson and 41-year-old Rhondo Robinson, both of Englewood, entered their pleas in federal court in Newark.

The U.S. Attorney for the District of New Jersey said the Robinsons’ failure to file resulted in nearly $1.3 million in tax losses to the government.

The men’s primary source of income was royalties from the label their parents founded in 1979, prosecutors said. The men also made money as copyright administrators for different recording artists.

The Sugar Hill label was best known for releasing “Rapper’s Delight,” rap’s first mainstream success. The company continued to play a part in the early years of hip-hop with a roster that included Grand Master Flash and the Furious Five. The label amassed an extensive music catalogue from 1979 until 1986.

The men’s mother, Sylvia Robinson, who had a hit as a singer-songwriter with the sexually charged “Pillow Talk,” and who some called “the mother of hip-hop” died in 2011.

Each of her sons pleaded to different counts Thursday, charging them with failing to file tax returns between the tax years 2005 through 2008.

Joseph Robinson pleaded guilty for failing to file taxes in 2005 and 2006, Leland Robinson for failure to file in 2006 and 2007, and Rhondo Robinson for his failure to file in 2005 and 2007.

Each defendant faces up to two years in prison and a $200,000 fine at their July 10 sentencing. They must also pay their back taxes and penalties, as well as the costs of prosecution