Becky Watts' stepbrother and his girlfriend have been named locally as the two people arrested on suspicion of her murder.
Nathan Matthews, 28, and his partner Shauna Phillips, 21, are still being questioned by police who were granted an extra 24 hours to keep them in custody yesterday.
Mr Matthews is the son of Becky's stepmother Anjie Galsworthy, the Daily Mirror reported, and the couple are believed to have a two-year-old daughter.
Avon and Somerset Constabulary said that Ms Phillips was taken to hospital overnight after feeling unwell in custody but returned after seeing a doctor.
Five other people, four men and a woman all aged in their 20s, were arrested on suspicion of assisting an offender after the 16-year-old's body parts were found at a house two miles from her family home.
Police were awarded an additional day to question the five by a judge at Bristol Magistrates' Court earlier today and they are still being held in custody.
Officers found Becky's remains in Bristol after receiving a tip-off on Monday night, more than 10 days after she went missing, telling them her body had been “cut up” and where to find it.
Investigators were seen removing wheelie bins and food recycling containers from the house in the Barton Hill area of the city yesterday, where children’s toys and a Wendy House could be seen in the garden.
Becky’s family spoke of their devastation when the grim discovery was announced after hundreds of volunteers joined police in huge search efforts and a social media campaign for information on her disappearance reached four million people.
Her mother, Tania, grandmother Pat and brother Daniel Watts, said they were “devastated”.
“We are at an utter loss to understand why anyone would want to hurt our beautiful Becky in such a brutal way,” they added, confirming that no one in custody was connected to their family.
In pictures: Becky Watts tributes
In pictures: Becky Watts tributes
A candle burns besides a photograph of Becky Watts at St Ambrose Church in Bristol
Flowers left outside Becky Watts family home are rearranged in Bristol
A teddy bear and floral tributes have been left near Barton Court in Bristol, as seven people remain in custody in connection with the investigation into the disappearance of teenager Becky Watts following the discovery of body parts
Flowers are left outside Becky Watts' family home
Messages are seen left beside a police cordon at Barton Court in Bristol
Becky's father, Darren Galsworthy, and step-mother Mrs Galsworthy said the news the teenager was dead was “too much to bear”, pleading for privacy.
“We are heartbroken…we cannot begin to understand what has happened and why,” her grandfather John Galsworthy added.
“Becky was a wonderful daughter, sister, granddaughter and niece, and we cannot put into words how devastated we are.”
Becky's brother, Dan Galsworthy, wrote on Facebook: "Can't believe what I'm hearing...this has left a deep hole in my heart and will continue to haunt me."
Detective Superintendent Mike Courtiour, of Avon and Somerset Police, said police had received “new information” late on Monday night that led them to her remains, although they have not yet been formally identified.
The teenager, described by her family as "shy", vanished from her home in Crown Hill on 19 February and was reported missing the next day.
She had taken her phone, laptop and tablet computer but did not tell friends or family where she was going or take extra clothes.
Flowers and tributes have been piling up near where her remains were found and at the gates of her home, where her family visited to lay their own bouquets in emotional scenes earlier today.Reuse content