Khadija, Sugra and Zohra Dawood, from Bradford, and their children aged three to 15 have not made contact for a week.
Their brother is understood to be fighting with extremists in Syria.
The fathers' lawyer said the children said "we can't wait to come home" in a conversation before they went missing.
Balaal Khan said: "We've had no answers whatsoever, we don't know what's happened."
Newsnight reporter Secunder Kermani spoke to Khadija's husband, who said he wanted to tell his wife: "I love you, please bring the kids back".
The fathers - two of whom are in the UK and one in Pakistan - have been "distraught, crying, they don't know what to do", said Mr Khan, adding it was suspected the women had taken their children to Syria.
The fathers last spoke to their children on 8 June, when they were in the Saudi city of Medina, said Mr Khan, adding: "They said 'We love you, we're missing you, we can't wait to come home.'"
Mr Khan said it was feared the sisters had met up with their brother - but stressed that while family members had confirmed he was in Syria, he could not comment on what he was doing there.
The case follows the deaths of Dewsbury teenager Talha Asmal, who reportedly blew himself up in Iraq, becoming the UK's youngest suicide bomber, and Muslim convert Thomas Evans, 25, from Buckinghamshire, who was among al-Shabab fighters killed in an attack on a Kenyan military base.
Police have said they are "extremely concerned" for the family's safety and that enquiries are continuing on a "national and international level".
The Bradford family travelled to Medina on 28 May and were last seen in a hotel in the city.
They were supposed to fly to Manchester following their pilgrimage but the fathers reported them missing when they did not return.
There has been no contact with the sisters for one week. Their mobile phones have not been active, nor have their social media profiles been updated.
Travel agents confirmed that 10 tickets were bought for a flight on 9 June to Istanbul in Turkey, a commonly-used route into Syria.
Mr Khan said it was not known whether the family had boarded the flight - or if two children who were unaccounted for - five-year-old Nurah Zubair and her sister Haafiyah Zubair, eight - were still with the rest of their family.
He said it was hoped all of the family were together and that a "computer glitch" could explain why the two girls were unaccounted for. He said he had asked for CCTV footage from Medina and from Turkey.
The 15-year-old son Junaid Iqbal was acting as the family's mahram - an appropriate male responsible for the family - during the Saudi pilgrimage, he added.
However, Mr Khan told the BBC the family did not feel they were getting the answers they needed from police and that they wanted a "special task team" designated to the case.
Meanwhile, Bradford West MP Naz Shah said she had spoken to two of the fathers and they were "worried out of their minds".
"I asked them if there was any indication [this could happen] and they said absolutely not - it was a shock to them, it came out of the blue.
"At this time there is no contact, absolutely zero contact with the women or children. The last contact was a few days ago when they were due to leave."
West Yorkshire Police have contacted the Turkish officials but there have been no sightings or contact made in Turkey.
A Foreign Office spokeswoman said: "We are in contact with West Yorkshire Police and Turkish authorities and are ready to provide consular assistance."
A neighbour of the family in Bradford, Mohammed Saeed, said it would be "devastating" if the family had travelled to Syria.
"They can't grow up in that kind of area," he said. "You hear about it all the time. All these people going there. It's just a hellhole there isn't it."
And Bradford East MP Imran Hussain said: "We have nine children that are missing at the moment and in particular some very young children, three and four-year-olds, and we need to ensure the safe return of those children."
The husbands of three sisters feared to have travelled to Syria with their nine children are said to be "distraught" after the group went missing following a religious pilgrimage to Saudi Arabia.