Hamas has held some Israeli hostages since long before Oct. 7.

The plight of families desperately seeking the return of their loved ones abducted from Israel on Oct. 7 is painfully familiar to Aviram Shaul.

His brother, Oron Shaul, was serving in the Israeli army when he was killed in 2014, during the last major war in Gaza. Israel says Hamas still has his body, along with that of Hadar Goldin, who was killed in the same war. The group is also believed to be holding two living Israeli civilians, Avera Mengistu, who crossed into Gaza in 2014, and Hisham al-Sayed, who entered Gaza in 2015. The Israeli government has said both suffered from mental health issues before they crossed out of Israel.

“Suddenly, over 200 families have joined the battle, and it’s a surreal spectacle that you were alone, lonely — just you against the world — and suddenly, another 200 families join you,” Mr. Shaul said in a recent phone interview.

The Shaul and Goldin families are actively supporting families whose members were taken on Oct. 7. They described feelings of frustration and abandonment after years of what they saw as failed attempts to pressure the Israeli government into securing the release of Mr. Shaul and Mr. Goldin’s remains. A spokesman with the Israeli prime minister’s office declined to comment.

“Almost 10 years, we’ve been in a never-ending battle to bring him back,” Mr. Shaul said. In a separate interview, Leah Goldin, Mr. Goldin’s mother, said, “We became the face of the failure to bring our hostages home.”

For the family of Mr. Mengistu, the renewed focus on hostages has offered one small glimmer of hope that the long quest for his release might be fulfilled.

Mr. Mengistu walked into Gaza in September 2014, shortly after a cease-fire. Hamas earlier this year released a hostage video appearing to show him calling for his release, the first public evidence that he might still be alive. Hamas released a video last year of the other civilian, Mr. al-Sayed, in a bed and wearing an oxygen mask.

The family of Mr. al-Sayed didn’t respond to requests for an interview.

“The country must take advantage of the current situation — it’s an opportunity that won’t repeat itself — to return Avera and all of the brothers and sisters who are captive in Gaza,” Ilan Mengistu, Mr. Mengistu’s brother, said in an interview last week, adding, “I wish we hadn’t gotten to this situation, but there’s no doubt that it gives hope, a little bit of hope.”

He said he felt the anguish of the newer hostage families.

“As much as we’ve been in pain and suffering for almost nine years, it’s hard,” he said. “I have no words, really, on how to encourage them. It’s really hard, but you can’t lose hope.”

The Goldin and Shaul families said they have held meetings with the families of the new hostages and connected them to various governmental bodies and trauma resources. The newer hostage families have been meeting with officials in Israel and around the world, hanging up posters and putting together public displays in many cities.

Ms. Goldin said she believed that the international community must do more, adding that countries that have pushed Israel for a cease-fire should also push more actively for the release of the hostages and that any aid into Gaza should be limited until the hostages are returned.

The Goldin and Shaul families are also determined to ensure that their relatives are not left behind. Mr. Shaul, in particular, has been concerned that hostage numbers released by the Israeli military since the start of the war have not included his brother.

“It’s impossible to separate between Oron and Hadar and the rest of the civilians and soldiers who were kidnapped,” Mr. Shaul said.