https://youtu.be/R_GVqSdYWUU?si=Iiy2icdr4MOdLTo- God does not want us to intermarry our close relatives. It is prohibited by God that we should marry our kins. As the people of God, obeying the instructions of God should be our priority. No matter the circumstances around us at where we are or what is obtainable in our culture, we should not disobey the commandments of God.
There are many things these days which are being practiced by so many people in different cultures of the world. There are traditions in which relatives intermarry themselves. That is the culture of men. We are to follow the teachings of God. Of course, these traditions are not compulsory for us. One has the right to accept them or to reject them. So, let us tilt towards obedience to God's commandments, not unholy traditions.
Scientific research has also revealed that marrying the same blood line causes generational sickness and afflictions to linger in the family lineage. When different blood lines are crossed, they produce stronger bodies. We need to look healthy. So, following good recommendations is good
Leviticus 18:6, 9-10 (KJV) None of you shall approach to any that is near of kin to him, to uncover their nakedness: I am the LORD. The nakedness of thy sister, the daughter of thy father, or daughter of thy mother, whether she be born at home, or born abroad, even their nakedness thou shalt not uncover. The nakedness of thy son's daughter, or of thy daughter's daughter, even their nakedness thou shalt not uncover: for their's is thine own nakedness.
Morally, I do not think that there is decency when we intermarry ourselves. It is not morally sound for siblings to uncover their nakedness.