ON April 17, 2006, a Palestinian suicide bomber killed 11 people near the old Tel Aviv bus station. Among the victims was Daniel Wultz, a bright and determined 16-year-old from Florida who fought for his life for 27 days before succumbing to severe injuries. His father, Yekutiel, who was wounded in the attack, watched the terrorist detonate himself. “I decided to do anything and everything I could,” he told me, “never again to have that helpless feeling.”

But almost nine years later, immense frustration has accumulated in Yekutiel Wultz, an Israeli citizen living in the United States, and his American wife, Sheryl Cantor Wultz (a cousin of Eric Cantor, the former House majority leader) over Israel’s actions since the death of their son and specifically over what they see as Prime Minister Benjamin Netanyahu’s abandonment of his cause.

They say there is evidence that the bomber who killed their son was backed by Iranian money that was laundered through China. Their feelings are running particularly high as Netanyahu prepares to address a joint session of Congress this week, where he will oppose a possible nuclear deal with Iran sought by President Obama. The family shares with the prime minister a deep distrust of Tehran, but they also feel betrayed. They are convinced that, in their son’s case, Netanyahu has placed Israel’s commercial interests with China ahead of punishing those responsible for their son’s death, in effect protecting Iran.

“He will be here to talk about Iran as a criminal, yet he’s trying to prevent us being successful in a lawsuit in which Iran is very much involved,” Sheryl Wultz said. “We would like to ask Netanyahu what happened to his morals.” She added, “We don’t believe there is any justification in protecting the facilitators of terrorists.” A senior Israeli official in the prime minister’s office in Jerusalem, asked if Netanyahu had sold the Wultzes down the river in exchange for the pomp of his China visit in May 2013, said in an email that this was “unequivocally incorrect.”