A 32-year-old man, who was arrested in connection with a flat fire on Anglesey in which two young brothers died has been released on bail.
The brothers were 'always smiling' said the family
Four-year-old Kyal Owen, who was due to start school on Tuesday, and brother Konnor, aged three, died of smoke inhalation.
An investigation is continuing into the cause of the blaze in Llanfaethlu near Holyhead at 0130 BST on Saturday.
A family tribute said the boys "were full of life and fun."
The first-floor flat, above The Coffee Shop in the centre of the village, was cordoned off as the investigation continued.
A tribute released by the family said: "Kyal and Konnor were full of life and fun. They were very happy children who were always smiling. Their parents and their large extended family loved them dearly."
The eldest Kyal was due to start school on Tuesday "but sadly will never get the opportunity to meet new friends and take part in activities and games that he so loved."
One man was treated in hospital for minor injuries
The family said although the brothers lived with their mother, they loved spending time with their father and "were mad about toy trucks and tractors."
It also spoke of their love of animals, playing on the beach, and walks with their grandfather and family dog.
The family were said to be "devastated by their tragic and untimely deaths."
A man, believed to be the boys' father, suffered minor injuries when he escaped and alerted emergency services.
The blaze left one room "extremely damaged" by fire, while other rooms suffered smoke damage, North Wales Police said.
A force spokesman said: "A 32-year-old man has been arrested in connection with the fire at a flat in the Llanfaethlu near Holyhead, Anglesey.
"We are not releasing any further information about this person's identity."
Post mortem examinations found the boys died of smoke inhalation. The coroner has been informed.