Saturday In-house Gist.... Marrying Within The Family

Marriage within the family seems to be more rampant in some regions of World for one reason or the other. Can you marry someone from your family?Like your Father's brothers daughter or son?or let siblings marry?Do you see these rela­tionships legally or socially acceptable?  Is there anywhere in the Bible that supports Marrying within the family? What is the Origin of allowing via IFTTT