The brothers killed their sisters, aged 20 and 27, in the capital of Amman earlier this week using axes to “cleanse the family honour”, according to officials on Wednesday.
A Jordanian official confirmed a report in the English-language Jordan Times that said the incident occurred after the younger woman fled home to live with her sister who had wed a man without her family’s knowledge two years earlier.
The deaths raised to at least 12 the number of women murdered by relatives to preserve “family honour”.
The crimes are committed usually by male members of the family who believe female relatives have conducted themselves in an inappropriate manner through alleged sexual relationships.
Jordan’s current penal code considers killing female relatives caught committing adultery as an act of self-defence, making sentences more lenient.
The House of Representatives rejected an amendment passed by the upper house or Senate that would toughen penalties for “honour killings” and sent it to the Senate’s legal committee for revision.
Activists said parliament’s rejection of the new law gave men “a licence to kill” their female relatives.
“After they rejected it in early August, three women were reported killing in 10 days. This is surely not a coincidence,” an expert was quoted as saying.