Why are people from Tamil Nadu generally darker than those from Kerala even though they are at the same distance from the equator?

It depends on which religion you follow.

Christian - NO (Can Cousins Marry in the Church? )

Hindu -marrying ‘Murapennu’ exist in certain community(nair’s specially).

Muslim - the system existed(not common now a days) Why does Islam allow and encourage cousins to marry? Is this still in practice?