Law enforcement officials tell TMZ Sports ... the older brother of NY Giants star Janoris Jenkins is a "person of interest" in the case of the dead body discovered at JJ's New Jersey home.
We spoke with Ontario County NY District Attorney James Ritts ... who tells us, "William Jenkins is a person of interest in relation to dead body case at his brother’s house."
"Bergen County wants to talk to him."
Here's the twist ... according to jail records obtained by TMZ Sports, 34-year-old William Jenkins was arrested in upstate NY on June 26 at 1:46 AM ET ... about 9 hours BEFORE the body was discovered at JJ's home.
It appears William was arrested for an unrelated parole warrant issue -- but now, investigators in the dead body case believe he might know something about the death of Roosevelt Rene.
Ritts tells TMZ Sports ... there will be an extradition process to bring William from Ontario to Bergen County, NJ -- which is about 300 miles away.
Important to note, William Jenkins is NOT a suspect -- officials just want to know what he knows.