Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori have been reunited with their families in the UK after years of detention in Iran.
The British-Iranian nationals were met by their loved ones at RAF Brize Norton in the early hours of Thursday.
Mrs Zaghari-Ratcliffe's seven-year-old daughter Gabriella rushed to hug her mother, who she had not seen in years.
Mr Ashoori's daughter Elika spoke of her happiness at seeing her father, sharing a video of the pair's arrival.
Gabriella was heard asking "is that mummy?" before her mother walked down the plane's stairs at the airport in Oxfordshire.
Mrs Zaghari-Ratcliffe, 43, and Mr Ashoori, 67, finally left Tehran on Wednesday after their release was secured following months of negotiations.
UK Foreign Secretary Liz Truss said the pair's departure from Iran had been uncertain until the last minute, but they were in good spirits.
MP Tulip Siddiq said Gabriella had asked her if her father Richard was "pulling her leg" about her mother coming home.
"My heart just broke," she said, adding that when she told her she was, Gabriella started playing the piano and singing.
Richard Ratcliffe's sister Rebecca said "a little girl has finally got her mummy and daddy back" alongside a picture of the family.
She told the BBC the two families had gone to a safe house and "Gabriella slept in between Richard and Nazanin for the first time in six years, so a very special moment".
She said she had had a message from her brother on Thursday morning and described him as "very buoyant".
He had said it was "lovely to be with his family again", she added.
It marked the end of an ordeal that saw Mrs Zaghari-Ratcliffe detained for six years after being accused in 2016 of plotting to overthrow the Iranian government.
She was sentenced to a further year in prison in April last year and a one-year travel ban on charges of propaganda against the government.
Mr Ashoori, a retired civil engineer, was detained in 2017 on spying charges and sentenced to 10 years in prison.
Both have consistently and vigorously denied the allegations.
Their release came after the UK settled a debt to Iran of almost £400m dating from the 1970s, when Iran ordered British tanks and armoured vehicles. After the Iranian revolution in 1979, the UK cancelled the order and Iran demanded its money back for undelivered vehicles.
On Wednesday, Ms Truss called this debt "legitimate" - adding that it and the detainees were "parallel issues in our bilateral relationship [with Iran]".
She said the money would be paid in compliance with sanctions on Iran, and ring-fenced for humanitarian purposes.
A third detainee, Morad Tahbaz, who has Iranian, UK and US nationality, remains in Iran although he has been released from prison. Ministers have vowed to continue to push for his return home.
The 66-year-old businessman and wildlife conservationist was accused of collecting classified information about Iran's strategic areas under the pretext of carrying out environmental and scientific projects, which he denies.
Ms Truss said she was pleased he had been released, but said the situation was "far from sufficient". The government would continue to work for his departure from Iran, she added.
Foreign Office minister James Cleverly told BBC Breakfast the Iranians considered his case more complicated because of his US citizenship - but said the British government did not and would continue to work alongside the US to secure his full release.
Speaking before Ms Zaghari-Ratcliffe's return to the UK, Mr Ratcliffe said he was "deeply grateful" for his wife's release and that it would be the "beginning of a new life" for their family.
He said Gabriella had picked out which toys to show her mother when the plane landed, and that one of the first things he would do was make his wife a cup of tea.
His parents Barbara and John Ratcliffe said they believed the family would be spending a few days in Foreign Office accommodation before returning home, but said they hoped to see them at the weekend.
Mr Ratcliffe had said he was worried about how untidy the flat was ahead of his wife's return and his father described it as "appalling".
His mother told BBC Breakfast there was a lot of campaign material as well as lots of toys which people had "generously" given to Gabriella.
"Maybe we should all be up there at the moment tidying," she said.
Ms Siddiq, the Labour MP for Hampstead and Kilburn, said there was going to be a period of adjustment for the family. "They are going to be different people... they have to get to know each other and Gabriella has to be able to trust her mother again," she said.