A relative says the young man at first was happy with the rebels, Ynetnews reported. But recently, after a month in Syria, he said he had been told "whoever joins us does not return to his family."
"He called me again and said he was very frightened, that both of their lives were in danger and they can't handle the situation," the relative told Ynetnews.
The Israeli Foreign Ministry said it has reached out to rebel allies in Turkey in an effort to find out what has happened to the two young men.
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