Four persons barged into a house in the Sambhal Kotwali area and opened fire on Suresh (23) and his father Dharampal, killing the former on the spot, a police officer said.
Dharampal was seriously injured in the incident and was referred to the Moradabad hospital for treatment, he added.
An initial probe had revealed that Dharampal's other son, Kripal, got married in April and his wife's "illicit" relationships led to the crime, said the officer.
The assailants, it appeared, had come looking for Kripal. When they could not find him, they fired at his father and brother, said the officer, adding that an FIR had been lodged against four unidentified persons in this regard.