My cousin had his 9th birthday as a Hamas hostage. I've no idea if he's dead or alive

• Itay Raviv, 27, is the CEO of a non-profit organisation in Israel. On 7 October, four of his relatives - including his nine-year-old cousin - were kidnapped by Hamas and taken into Gaza. Another cousin was killed in the attack on the Nir Oz kibbutz.

• Israel has agreed a hostage exchange with Hamas that will see 50 people freed in exchange for a four-day ceasefire and 150 Palestinian prisoners in a deal brokered by Qatar with the support of the US. The exchange, due to take place today, hit a last-minute snag and was delayed.

(This interview took place the day before hostages were due to be released.)

My cousin, Ohad, celebrated his ninth birthday in captivity. That is something that still - seven weeks after he was taken - I can't imagine. He had planned a party for his friends, but never got to go. He's such a special and smart kid, it's hard to believe this has happened.

We have no idea if Ohad, his mother, Karen, and grandparents Ruthi and Abraham are among the 50 people due to be released - since the massacre all we know is that their mobile phones were geolocated to Gaza. Hamas hasn't provided the Red Cross with a list of hostage names so we don't even know if they're alive.

My aunt and uncle, Ruthi and Abraham Munder, are both 78 years old, and have lived in kibbutz Nir Oz for almost 60 years. They had a small family - just one daughter and one son, Roee, 50, who was murdered on that Saturday morning. Ohad is their only grandson, and he and his mother were visiting them in the kibbutz for the Jewish holiday.

They found themselves in this horrific terror attack - the last we heard from them was at 9.58 on the Saturday morning. Ruthi spoke with her sister - she whispered into her phone: "We can't talk, there are terrorists inside the kibbutz."

Nobody thought anything like this would happen. On the Saturday morning, there were sirens all over Israel, as missiles and rockets were being fired at the same time. Usually when there are bombings, we go to the shelter, and text our family to say 'are you OK?' and afterwards everyone goes back to normal - which itself is absurd, because what's normal about being targeted by missiles?

But on this Saturday, we understood that it was different, just the sheer magnitude of the attack.

Then our family texted us that they could hear gunshots nearby, and after Ruthi told us they were inside the kibbutz, that's the last we heard from them.

Around an hour later, their phones were geolocated in Gaza - we didn't know this at the time. When we lost contact with them we just thought it was because of the internet connection or a power outage. It was only when we saw the videos circulating on Telegram of the horrors in the kibbutz that we realised what had happened.

After police told us their phones had been located in Gaza, our assumption was that they have been kidnapped. They didn't find their bodies in the kibbutz but we have heard nothing since.

It is seven weeks now and we don't know their condition. My uncle is not in very good health; he barely walks, he barely sees and needs to take medication daily. We don't know if he receives any of it. We don't know if they're alive or not, it's crazy.

The phones tell nothing apart from where the phones are - but because it's all the same time and around the same place, we assume they have been kidnapped, Again, Hamas hasn't even provided the Red Cross with a list of the hostages - this is a crime against humanity that is ongoing.

This is kids - Ohad had his 9th birthday a few weeks ago. We had a campaign throughout Israel where people put a balloon outside their homes for his birthday, so that everybody knows him and nobody forgets about him. Since then, there have been so many birthdays of kids, of people who are in captivity - there was another girl on Friday who had her 9th birthday.

We have been talking to the press and politicians throughout the world, we have been protesting in Israel - we've been doing everything we can, speaking to anyone who will listen - and some people are not willing to listen - just to share their stories and share the faces and the names behind the numbers because this is something the world cannot stay silent to. This is a crime against humanity.

Kids and innocent civilians were taken from their homes, from their beds in their pyjamas on the Saturday morning of a Jewish holiday. I keep thinking about my family, who all wear glasses, and I don't even know if they have their glasses on.

My mission as a family member is to make sure nobody loses focus about my family. Hearing about the hostage deal, it makes me feel like it gives legitimacy to the act of kidnapping civilians, but we value life and we want to make sure people live.

Of course it also gives us hope - there is always hope. If there wasn't hope, we wouldn't be able to function. Hope is what keeps us going as Jewish people, it is something that's in our roots and gives us fuel to function.

The deal is only 50 people - and we want to see all 240 returned. We need all of them back, they have done nothing wrong and we must not forget about them.

We missed Ohan's birthday. When he comes back, when they all come back, we're going to have a birthday every day.

Words told to Harriet Sinclair