A father-son duo and one of their close relatives were brutally murdered and two others injured while they were asleep at their house in east Delhi, police said on Tuesday.Ram Kishan, in his late 50s, his son Raju and Ram Kishan's son-in-law Kishan Pal died of injuries inflicted with blunt weapons on Monday night. Tarun, 25, and Vineet, 14 were injured. According to police, the five were sleeping on the roof of their two-storey house in Nand Nagari while the female members of the family were sleeping downstairs."All five were attacked with a wooden log or iron rod on their heads," a senior police officer told IANS."Tarun is critical but Vineet is out of danger," the officer added.The officer said it was early to comment on the motive behind the murder. "We have taken a person in custody and are questioning him."The officer said there was no evidence of forced entry into the house.