Two teen brothers wanted in connection with an attack on an 83-year-old Pinellas Park man remained in juvenile detention on Thursday.

The oldest, 16-year-old Antonio Peterson, appeared in court Thursday on an aggravated robbery with a deadly weapon charge.

His younger brother, who is not being named because he is 13, faces a grand theft charge.

After turning himself in to authorities late Wednesday, police said he admitted to helping steal Charles Clark's car but did not participate in the attack earlier Tuesday.

Police said the two St. Petersburg brothers, along with a 15-year-old girl, attacked Clark about 10 a.m. Tuesday as he was getting out of his car at his Pinellas Park condo complex. As Clark fought him off, he said Peterson slashed at his arm with a knife. The teens left with his keys, and that night his car was stolen as he slept. Four bikes were found nearby.

The girl was in custody Thursday night, police said in a news release. It was unclear what charges she will face, so she also is not being named.

Clark was badly bruised in the attack and also had a fractured cheekbone and several stab wounds in his arm.

On Thursday, he said he was glad to see the brothers in custody.

"He could have killed me," Clark said of Peterson. "He could have killed someone else.

"I want all three of them in jail."

Police said they expect more charges for both brothers.

During an initial hearing for the oldest brother Thursday, the teens' grandmother and father attended.

"I can't understand what went wrong," said Georgia Murphy, their grandmother.

Their father, Antonio Peterson, 37, said he feels sorry for Clark.

He said his sons are close, but he has warned them to watch the crowd they're hanging around. "They're good people," he said of his boys.

The father and grandmother stood before County Judge Lorraine Kelly, who told the oldest teen she would appoint a public defender for him and that, for now, he would be kept in custody.

Peterson asked when his younger son's hearing would be. The judge said it would likely be today and offered to sign a letter excusing him from work.

"I'm sorry that you have to come back," Kelly told the father.

Clark was resting at home Thursday. Walker Ford has offered free repairs to his Ford Fusion, which was damaged in the theft, and the locks on his home have been replaced.

Claire Wiseman can be reached at cwiseman@tampabay.com or (727)-893-8804. Follow @clairelwiseman on Twitter.