Scott Snowden, on trial for the death of Thomas Sharkey, 55, at his home in Helensburgh, Argyll, wanted to cause a “family rift”, a friend told the High Court in Glasgow.
Mr Sharkey’s wife Angela, 48, survived the fire which claimed the lives of the couple’s eight-year-old daughter Bridget and son Thomas jnr, 21.
Snowden, 37, and Robert Jennings, 50, deny murder and attempted murder by setting the fire on July 24 2011.
Witness Lee McCarthy, 31, said that, during a conversation in the pub, Snowden told him he planned to get Mr Sharkey shot.
“He says he was going to get Mr Sharkey shot so his cousin Mark Sharkey gets the blame of it,” Mr McCarthy told the jury.
The witness agreed when judge Lord Matthews asked if the motive appeared to be to “cause some rift in the family”.
Unemployed Mr McCarthy, released last week from a jail term for charges relating to supplying cocaine, was giving evidence for a second day.
The court heard that after the conversation Mr Sharkey organised a charity event at the town’s Victoria Halls.
He said he told Snowden a week after the event: “I thought he was getting shot.”
McCarthy said Snowden replied:”I’ve got something else in mind for him.”