Cameron Logan, 23, died in a blaze at his family home in Milngavie on January 1. His girlfriend, Rebecca Williams, was seriously injured.
Blair Logan, 26, was in police custody last night, the Record reported. The Scottish Sun said the arrest came after detectives confirmed they were following a definite line of inquiry.
Meanwhile, the Scottish Daily Mail leads with news that the number of people working into their 80s and 90s has doubled in the last five years.
Jeremy Corbyn needs to raise his game north of the border if Labour hopes to regain power in 2020, shadow Scottish secretary David Anderson has told The Herald.
The Scotsman reports that a row has broken out over a major report on Brexit after MPs blocked calls for the Scottish Parliament to get a vote on the UK's final deal with Brussels.
The Queen has been left "saddened" by the death of her former brother-in-law, Lord Snowdon, according to the Daily Express.
Under the headline "Let's Do This", The National's front page promotes a series of reports ahead of the Scottish Independence Convention in Glasgow.
The Press and Journal reports that events across the north-east could be cancelled if Aberdeenshire Council "forces through" a 700% increase in the cost of entertainment licences.
A "landmark" prosecution has been launched against the former owners of shops selling drugs which were once known as "legal highs", according The Courier.
The arrest of the brother of a man who died in a fire on New Year's Day made the front page of later editions of both The Daily Record and The Scottish Sun.