Noiya, 16, and Yahel, 13, vanished during the militants’ horrifying day-long rampage through Kibbutz Be’eri – just 4km from the Gaza border.
The teenagers’ mum Lianne, 48 – who was from Bristol but moved to Israel when she was 19 – was tragically found dead.
Their Israeli dad Eli, 51, is also missing.
Eli’s brother Yossi was snatched by gunmen from his nearby home in the kibbutz and was last seen being driven away.
At least six British citizens have been killed in Hamas’ brutal attacks on Israel, Rishi Sunak confirmed on Monday.
The Prime Minister also confirmed a further ten Brits are missing and feared dead as he insisted: “We stand with Israel.”
The family of Yahel and Noiya fear the girls have been taken to Gaza as hostages – where Hamas are using civilians as “human shields” to fend off Israeli forces.
Their uncles, Raz Matalon and Sharon Sharabi, told Mail Online that Israeli troops found gunshots in the bomb shelter of their family home and “two big blood stains” on the floor of the girls’ room.
“We don’t know anything else about the girls and about Eli,” they said.
“The three of them are considered to be missing.
“Lianne was declared murdered so we are arranging a funeral in our village.
“We are not eating, we are not sleeping. We are doing everything we can to make their story heard and bring them home.”
They said Yossi “struggled to hold the door handle” as the terrorists stormed inside, “took the family outside and burned their house”.
Raz, Eli’s brother-in-law, told The Times: “We want to send a message that we want the British government to take some action to at least find out what happened to the girls.
“We don’t know if they were kidnapped but if we come to that point, we would be happy if they try to do whatever they can to bring those girls back home.”
In a tribute shared with the BBC, Lianne’s family members said she “enriched the lives of all those lucky enough to have known and loved her”.
‘She lived a beautiful life and will be sorely missed by the heartbroken family and friends she leaves behind,” they said.
Hundreds were killed and dozens taken hostage when Hamas gunmen burst across the border on paragliders and motorbikes on October 7.
As families of some of those missing watched on, Mr Sunak told the Commons on Monday: “The attacks in Israel last weekend shocked the world.
“Over 1,400 people murdered one by one, over 3,500 wounded, almost 200 taken hostage.”
He went on: “The elderly, men, women, children, babes in arms, murdered, mutilated, burned alive.
“We should call it by its name: it was a pogrom. The families of some of the missing are in the public gallery today.
“We call for the immediate release of all hostages and I say to them: we stand with you. We stand with Israel.
“The murdered and the missing come from over 30 countries, including the United Kingdom.
“The terrible nature of these attacks means it is proving difficult to identify many of the deceased but with a heavy heart I can inform the House that at least six British citizens were killed.
“A further ten are missing, some of whom are feared to be among the dead.”
Mr Sunak also insisted “we stand with British Muslim communities too”.
He said: “I also recognise that this is a moment of great anguish for British Muslim communities who are also appalled by Hamas’s actions but fearful of the response.
“We must listen to these concerns with the same attentiveness.
“Hamas is using innocent Palestinian people as human shields.”
It comes as the UK last week ordered rescue flights to bring Brits back.
Mr Sunak said today: “We’ve organised eight flights so far, bringing out over 500 people, with more flights leaving today.
“We are working with neighbouring countries on land evacuations for our citizens in Gaza and the West Bank.”
As it stands, four British citizens killed in Israel have been named.
Jake Marlowe, 26, was working as a security guard at a music festival when it was stormed by Hamas gunmen who turned it into a bloodbath.
The Nova music festival was the first target of Hamas terrorists as they paraglided across the border into Israel and unleashed terror on unsuspecting festival-goers on October 7.
The Londoner’s parents, Lisa and Michel, said they were “heartbroken” after receiving the “crushing news”.
Horrified rescuers found 260 bodies after Hamas terrorists cut the power and opened fire.
Only hours before the gunmen unleashed hell, Jake – who moved to Israel two years ago – had sent a text to his mum saying rockets were flying overhead and promised to keep in touch.
Scot Bernard Cowan, 57, was murdered by the terrorist group during the horror attacks.
And Corporal Nathanel Young, 20, who was serving in the Israeli Defence Forces, was confirmed dead on Saturday.
Daniel Darlington, 34, a UK photographer, was also killed while visiting the country.
His sister wrote on Instagram that he was “murdered by terrorists”.
Hamas militants also took captives during their bloody massacre – and the Israeli military says some 199 hostages are being held in Gaza.