Ravi Vishwakarma and Aatish Verma had stabbed the victim Shubam Chouhan (16) to death in Bhagirathpura area of the city on July 29, said ASP (east) Abid Khan.
The duo have also admitted to murdering Om Prakash Yadav (43) in Sunder Nagar area on July 6, they said.
Besides Vishwakarma and Verma, three others were also involved in Yadav's killing and were already apprehended, they said.
Explaining the modus operandi, police said the accused would target people riding cycles in deserted areas and loot valuables and cash from them.