No one said there is anything wrong with that but Somalis keep it very close and some cases were marriages within the family themselves. Also Allah SWT never said marry from your first cousin it's best marriage there is. It's permitted but no one encourages it. A lot of scholars recommend marrying non relatives.fk out here marrying cousin nothing wrong about it prophets did all the people in the past did it and modern people still do it
it isjust when you do every single generation that is when it become problem