Relatives With Whom It Is Obligatory to Maintain Ties of Kinship With
14-10-2020 | IslamWeb
Question:
If I understood correctly, there are two opinions about who the relatives that ties of kinship must be upheld with are - mahram relatives e.g. siblings and uncles, OR any relative you have blood ties with. I'm confused about this second one because technically we have a blood tie with every human on earth? So where would it end? 2nd, 3rd, 4th cousins? I understand that the relationship with your sibling is very different to your relationship with the more distant relatives but am still confused
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
Those who held that the relatives with whom it is obligatory to uphold ties of kinship are not only the Mahram relatives mentioned that non-Mahram relatives with whom it is obligatory to maintain ties of kinship are “Thawoo Al-Arhaam”, i.e. the relatives who are not entitled to inherit by either Ta‘seeb or by a fixed share. An-Nawawi 
said in his commentary on Saheeh Muslim: "It was said that this applies generally to all relatives who are included in the category of Thawoo Al-Arhaam with regard to inheritance." [End of quote]
The Thawoo Al-Arhaam relatives in this subject include all relatives who do not inherit by a fixed share or Ta‘seeb, such as the maternal grandfather (the mother’s father), the daughter’s children, and the like.
Non-relatives are not included in the category of Thawoo Al-Arhaam. The wife’s relatives, for example, are not included in this category with respect to the husband, but they are rather classified as his in-laws, and the same applies to the wife’s relationship with her in-laws; they are not among her relatives unless the spouses are related, as is the case when a man marries his cousin and the like.
The in-laws may not be classified as relatives based on the fact that they are all the children of Aadam; none of the people of knowledge has ever held such an opinion.
Allah Knows best.