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 Ontatio 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 26th at 1:46 AM ET .