Cameron Logan, 23, died in the blaze in Milngavie on 1 January, while his partner Rebecca Williams, 24, was seriously injured.
Blair Logan, 26, has been arrested in connection with his brother's death and the alleged attempted murder of his parents, both aged 54, and Ms Williams.
He is due to appear at Dumbarton Sheriff Court on Monday.
Ms Williams, a journalist with Global Radio, was initially taken to the Queen Elizabeth University Hospital in Glasgow in a critical condition.
She was later transferred to the Glasgow Royal Infirmary where she is now said to be in a stable condition.
The house in Achray Place remained cordoned off on Saturday with large green covers still in place over the property.
Police officers stood guard at the front and back of the semi-detached house and fresh flowers left in tribute to Cameron Logan were placed around a tree outside.
Police have arrested the brother of a man who died in a house fire in East Dunbartonshire on New Year's Day.