One of the two men arrested in connection with the terror incident on Friday has been identified as 21-year-old Yahyah Farroukh, and is listed as living at an address in Stanwell, Surrey, which was searched by officers on Sunday.
He was arrested at a fried chicken shop in Hounslow on Saturday night.
He was the second man arrested. Another 18-year-old was detained at Dover ferry port on Saturday morning.
The younger man is suspected of planting the device, which exploded on a District Line train on Friday morning, injuring 30 people.
Police said the two men are being questioned on suspicion of offences under the Terrorism Act.
Both men are believed to have spent time in the care of Penelope and Ronald Jones, who received MBEs for services to children and families in 2010.
Sky News understands that Mr Farroukh has a number of links to the Joneses.
He is linked with Penny Jones via Facebook and is also one of the people most recently registered to the address where the couple live.
They have been highly respected foster parents for almost 40 years and looked after up to 300 children, including eight refugees.
Leader of Spelthorne Borough Council Ian Harvey, whose ward is Sunbury East, said the 18-year-old is understood to be an Iraqi orphan who moved to Britain when he was 15.
Mr Harvey said: “One thing I understand is that he (the 18-year-old) was an Iraqi refugee who came here aged 15 – his parents died in Iraq.”
Of the other suspect, he said: “I think it is widely known that this person who lives at (the Stanwell) property was a former foster child at the property which was raided.”
Mr and Mrs Jones’s home in Sunbury-on-Thames was searched by armed police on Saturday morning and is still being examined by counter-terrorism investigators.
Footage has emerged of a man in Sunbury carrying a Lidl bag, similar to the one the suspected device was hidden in, around an hour-and-a-half before the attack.
The man was seen on camera at 6.50am reportedly leaving a house which police later searched.