Marriage With Mother's Cousin
First we need to understand what is the domain of religion and why religion addresses that particular domain only. The purpose of religion is Tazkiya of human existence. Human existence can be further delineated into following aspects and hence the required Tazkiya is related to the same aspects namely: – Purity/tazkiya of body – Purity/tazkiya of food – Purity/tazkiya of soul (ikhlaqi tazkiya/ethics) – And for the growth of this tazkiya there are ibadah/worship rituals All the directives of Islam address these specific aspects of our Tazkiya because this is the kind of Tazkiya required for our success in the hereafter, God is selecting pure souls to hand them over a part of His eternal kingdom. That is why, regarding social directives ( including marriage, divorce, moharramaat etc. ) only those issues were addressed which were required to achieve ikhlaqi tazkiya/ethics, both from the perspective of an individual and at times, from the perspective of the whole society. Rest of the matters, including medical, biological, nutritional pros and cons of an activity, customs, food etc. have been left to the intellect of human beings which they can decide on the basis of their years of experience and scientific progress. Therefore, from an Islamic perspective, there is no bar on cousin marriages, it is left to humans to decide this based on their medical progress that which course of action they want to pursue and which course of action they want to avoid. Following videos will add further insight into this matter: Please refer to the video below from 26:55 to 29:54 https://youtu.be/6tZYLtAIhGA?t=1615