(NewsNation) — As the Israel-Hamas ceasefire deadline to release all hostages nears, the family of Nimrod Cohen, who was a 19-year-old Israeli soldier at the time of his capture, pleaded with U.S. lawmakers Thursday to advocate for his release.

Under the first phase of the ceasefire, Hamas agreed to release 33 hostages, of whom 16 have been released so far. Cohen was not one of them, though his family told NewsNation they had received “proof of life” two weeks ago and so they felt optimistic.

“We have a very deep fear that this ongoing hostage deal will collapse somehow,” Nimrod Cohen’s brother Yotam Cohen told “NewsNation Now” host Connell McShane.

Yotam Cohen and his father, Yehuda Cohen, made their fifth trip to Washington, D.C., on Thursday to push lawmakers to advocate for Nimrod Cohen’s release.

“We have to go to international sources to force our government to do its duty. Its duty, by law, is to secure the life of Israeli citizens and soldiers,” said Yehuda Cohen.