Two brothers, identified as Falak Niaz and Altaf Niaz, shot dead the three persons, including their brother and his wife.
Umar Khan, a resident of Mathra area of Peshawar, said two of his sons killed his third son Muntazir Khan, daughter-in- law Afshan and her brother Fatah Mohammad as they were upset with the marriage.
Acting on a complaint from Khan, police arrested Altaf.
Such "honour killings" are banned in Pakistan but the number of reported cases is rising.
According to statistics from Aurat Foundation, a leading NGO working on women's issues, 432 women were reportedly killed in the name of honour in the country in 2012.