Ex-model Kayden Nguyen is suing the Under Siege actor for $1 million (£666,000), claiming he used her "like a sex toy" and expected her to pleasure him sexually after landing a job as his executive assistant.
Two unnamed women have submitted sworn declarations to help Nguyen's case - and now one of the alleged victims has been revealed as Charles' granddaughter Blair Robinson, according to TMZ.com.
In Robinson's declaration, she claims she first met Seagal at Ray Charles' 2004 funeral and took on a job as his assistant one month later.
Robinson alleges she quit after one day when Seagal made inappropriate sexual advances. She said the actor told her she was required to give him massages and he tried teaching her the proper method by massaging her.
She states: "It became clear to me that he wanted and expected sexual favours as part of my job duties."
Seagal's lawyer, Marty Singer, has denied the accusations and claims Seagal has "no knowledge" of Robinson or the other woman who has come forward with similar statements.
He added, "The declarations were clearly prepared by Nguyen's lawyer to be leaked to the media to help bolster his client's meritless claims."
Seagal's reality show, Steven Seagal Lawman, has been put on hold following the allegations.