The bible made us to understand about boundaries in our household most especially relatives who are close to us. In the scriptures God gives detailed instructions that forbids marriage or sexual relations between close relatives such as children, parents, siblings, aunts, and uncles.
These instructions were given to preserve moral order, respect within families, and also to maintain the health of the community. Such unions are recognised to be improper and dishonoring unto God.
Although initially the bible did not forbid us from marrying all close relatives. For instance, marriage between more distant relatives, like cousins, is not specifically condemned in the bible. There are biblical figures; the likes of Isaac and Rebekah, were related within the extended family.
This tells us that while close blood relationships were originally restricted, wider family connections were sometimes acceptable based on cultural and historical contexts.