She also leaned forward and identified the Grammy winner as the same man she saw on a sex tape at the center of the trial.
Before testifying, Edwards watched the videotape; during testimony she said she was sure her relative appeared on it having sex with Kelly.
"You know your blood ... you just know your family," she said.
The testimony is part of prosecutors' attempt to prove to the jury that the two people on the 27-minute homemade video are Kelly and the alleged victim. Both he and the female - now 23 years old - have denied they are in the footage.
Kelly, 41, is charged with 14 counts of child pornography for allegedly videotaping himself having sex with an underage girl. He has pleaded not guilty and faces up to 15 years in prison if convicted.
Edwards, who was a background singer on one of Kelly's albums, testified that her relative was fond of Kelly and "took to him as a father figure."
Cross-examination of Edwards got heated, with the defense grilling her about a falling out she had with Kelly around 2000, two years after Kelly produced her debut album.
Defense attorney Ed Genson suggested Edwards - whose stage name is "Sparkle" - may have hatched a plot aimed at "getting Robert," referring to Kelly's given name.
"Of course not, " Edwards responded. "I was cool with Robert."
Genson and Edwards talked over each other at one point. Genson suggested Edwards may have tried to squeeze money out of the R&B superstar.
Edwards replied with a raised voice: "Sweetie, I'm not trying to get money out of this."
"I'm not your sweetie!" Genson shouted into a courtroom microphone, the room booming.
At that point, Judge Vincent Gaughan intervened and told both Edwards and Genson to calm down and stop talking over each other.
"This is a court of law," Gaughan said.
Earlier Thursday, a college student testified that she recognized both the female in the tape and Kelly, saying the female was a minor when the video was made.
Audrey Hampton testified Thursday she played basketball with the alleged victim and went to school with her for several years. She told the jury "there's no question" that the female on the tape is her childhood friend at age 13 or 14.
Hampton, a 23-year-old senior studying business marketing at the University of Wisconsin-Milwaukee, also said the alleged victim introduced her to Kelly at a party at a downtown Chicago basketball court. She said that rumors started to spread in her neighborhood about a sex tape with her friend in it.
Asked by a prosecutor how she recognized her friend, the witness said she recognized her face, voice, as well as some of her mannerisms in the tape, including "the way she licked the bottom of her lip."
Under cross-examination, Hampton conceded that she wouldn't be able to recognize her childhood friend's body.
Hampton's mother, Mary Kay Jerit, testified earlier in the day and said she found the sex tape in her daughter's room in early 2000. She said she viewed parts of it herself, and then threw the tape into the garbage.
Sam Adam Jr., one of Kelly's attorneys, asked Hampton and her mother if they handed over the tape to authorities that they suspected was child pornography. Both women conceded that they had not.
Adam has told the jury that neither Kelly nor the alleged victim are the two people on the tape.
Thursday's testimony followed an incident and the arrest of a 48-year-old woman who screamed "Free R. Kelly" at the jurors in the case as they stepped off an elevator near the courtroom.
Police immediately grabbed Debra Triplet and led her away in handcuffs. Gaughan later ordered her held on contempt charges in lieu of $50,000 bond.
Gaughan asked jurors before the proceedings if they'd heard what the woman had screamed. None of the jurors said they'd heard her, and testimony continued.
