By Michael Martinez
"If you're alive, turn yourself in and ask for forgiveness from the victims," Tsarni said in front of reporters in a press conference outside his Montgomery County, Maryland, home.
Dzhokar Tsarnaev, 19, is the subject of a massive police dragnet in the Boston area. His brother, Tamerlan Tsarnaev, 26, died after an overnight shootout with police.
The brothers come from an ethnic Chechen Muslim family, and Tsarni said the two nephews brought shame to his brother's family. The nephews are sons of Tsarni's brother, and Tsarni last saw his nephews in December 2005.
"You put a shame on our entire family -- not our family, the Tsarnaev family -- and you put a shame on the entire Chechen ethnicity," Tsarni said.
CNN's Jaclyn Wang contributed to this report.