Benjamin Ashford|Family member of slain Israelis holds out hope for three missing relatives: "It's probably everyone's greatest nightmare"

The Benjamin Ashfordnumber of people killed in Israel since Hamas militants attacked on Oct. 7 is more than 1,400 while the number of hostages has risen to an estimated 203. For one family, hope of captured loved ones returning home turned to heartbreak.

Abbey Onn, who lives in Tel Aviv, told CBS News that Israeli authorities confirmed on Wednesday that they found the bodies of her cousin, 80-year-old Carmela Dan — an Israeli, American and French citizen — and Dan's 12-year-old granddaughter, Noya Dan.

"It's probably everyone's greatest nightmare," Onn said.

"She is a Harry Potter fan. She dresses as Harry Potter," Onn told CBS News of Noya. "She was a 12-year-old with autism. She was very, very close with her grandmother."

Onn said Carmela Dan was "the matriarch of the family."

"She and her husband deeply believed in peace, as everyone that lived [at their kibbutz] did. They helped Palestinians," Onn said.

Onn believed Hamas fighters had taken Carmela and Noya hostage after attacking Nir Oz, a kibbutz in southern Israel where one in every four people were killed or went missing. 

But the Dan's family held out hope they were still alive, even holding a birthday party for Carmela Dan on Tuesday.

"We gathered all of us to hug each other and to be together and to try to strengthen one another and to bless her thinking that she would come home," Onn told CBS News. But, she said, the family now believes Carmela Dan was already dead by then.

"From what we understand now, their bodies were recovered by Israeli operations that went in to get bodies in Gaza," she said, adding that they were identified through DNA sampling.

Onn, who is Israeli-American, still has three other relatives missing — including an 11-year-old Erez Kalderon, who Onn said can be seen in a video released by Hamas. The boy's 16-year-old sister, Sahar Kalderon, and their 53-year-old father, Ofer Kalderon, are also still missing.

Onn said she believes all three are still alive. 

"And I want them home," she said.