Gardaí confirmed they are investigating a fire at a house at Barnamore Crescent, Finglas, that was started in the early hours of Saturday.
It is understood James Whelan’s mother Sonya and another son managed to escape the house uninjured after the attack, which took place at 2am.
The house was substantially damaged, as were two cars parked outside.
Gangland murder victim Whelan (29) was shot dead on April 3 on the orders of a Kinahan cartel-linked criminal known as ‘Mr Flashy’, as part of an escalating local drugs feud.
The arson attack targeting the dead man’s mother and brother this morning is also believed to have been carried out by Mr Flashy’s gang and will “significantly heighten simmering tensions”, security sources say.
“This is a very serious escalation in this feud. Two people could have easily been killed in that fire,” a source said.
"Finglas is going to be like a tinderbox after this reckless arson attack. There will undoubtedly be retaliation from criminal associates of Whelan over this sinister attack on his innocent family.”
It is understood that Garda patrols in Finglas will be stepped up this weekend as officers fear retaliatory attacks.
Garda headquarters confirmed the arson attack when contacted, saying: “Gardaí responded to reports of a fire at a residence in Finglas, Dublin 11, that occurred in the early hours of this morning.
“Emergency services also attended the scene. Damage was caused to the entrance of the property and two vehicles parked nearby. The scene is currently preserved for a technical examination. No injuries were reported by the occupants of the premises.”
Whelan was shot dead in the Deanstown Avenue area in the early hours of April.
The convicted drug dealer was once a key member of the ‘Mr Flashy’ crime network but had broken away from the gang to set up his own criminal enterprise. He was a senior player in a gang of young dealers using electric bikes and electric scooters to deal crack cocaine and cannabis in the northside suburb at the time of his death.
This brought him into direct confrontation with ‘Mr Flashy’. Whelan and his gang had been subjected to threats and taunts on social media in the months before he was murdered, after a number of escalating violent feud incidents in Finglas.
The elaborate gangland funeral of the father-of-one last month saw him buried in a gold coffin and also featured scrambler bikes, a saxophone player and dancing mourners.
The event was recorded for posterity in a video posted by O'Dwyer & Sons Funeral Directors who said: "We would like to pass on our deepest condolences to the family of young James Whelan and the biggest thank you for choosing of taking care [sic] of their loved one. RIP Whela."
The professionally shot video begins with aerial footage showing a temporary marquee set up near his home with people crowded outside on the streets.
The filming then descends to street view where dozens of bikers in high-vis yellow vests are seen revving up scrambler bikes amid clouds of smoke.
Mourners are also depicted preparing the horse-drawn carriage with flower displays featuring the words ‘Brother’, and ‘me mate’.
A dog in a cut-off tuxedo and black dickie bow is led on a rope while men in black top hats gather together the horses to pull the carriage.