Well will reply to your comment about why only men, later but i think if you take up Hinduism or Indian culture you see there is this ridiculous tradition of not allowing same gothra marriages. It is as ridiculous as anything when they kill a boy and girl just because they are from same gothra and still dared to marry
You are absolutely right.This is indeed ridiculous.The only saving grace is that in my country this is illegal and the law forbids any such discrimination,and further this has no place under the Hindu marriage Act.Refer the link below,where the Khaps are trying to get the HMA amended,but that day will never come.I don't know if in pakistan,your Marriage Act is any different from what the religion has pre-ordained.
SC refuses to hear PIL against same gotra marriage