Imam Hassan al-Mujtaba (a.s.) said:
اَلْقَريْبُ مَنْ قَرَّبَتْهُ الْمَوَدَّةُ وَ إنْ بَعُدَ نَسَبُهُ وَ الْبَعيدُ مَنْ باعَدَتْهُ الْمَوَدَةُ وَ إِنْ قَرُبَ نَسَبُهُ
Near kinsfolk are those who are more affectionate, although they may be genealogically not as near as those who are less affectionate.1
Kinship is one of the most important social relations in Islam . It enables formation of well-knit groups in the heart of great human society whose members cooperate closely and help each other in solving critical problems.
The criterion of relationship in Islam , as stated in the above tradition, gives much importance to affection and friendship, not merely the closeness of genealogical relationship.