Scott Snowden,37, and Robert Jennings,50, were told they would go on trial at the High Court in Glasgow in May.
The pair are accused of murdering Thomas Sharkey Snr,55, his daughter Bridget, eight, and his son Thomas Jnr,21, at their home in Helensburgh, Dunbartonshire, in July 2011. They are also accused of attempting to murder Mr Sharkey's wife Angela,47,.
Snowden, a prisoner of HMP Barlinnie, and Jennings, a prisoner of HMP Edinburgh, face a total of 23 charges for alleged arson, breach of the peace, assault and drug dealing offences.
Prosecutors allege the pair poured petrol through the letter box of the door of the Sharkey's property in the town's Scott Street.
Lawyers acting for the two men told Lord Uist at the High Court in Edinburgh that they hadn't yet fully prepared their cases.
They asked the judge to set another procedural hearing for April 22 at the High Court in Glasgow.
Lord Uist agreed to fix another hearing for that date - Lord Matthews will preside over proceedings then.
The judge also fixed the trial date for May 7 and said he expected the case to last eight weeks.