I checked the website that 雲小泉 gave and it did not give enough information. I was not very happy with that website. The word "kin" is a cognate in several earlier languages and can be traced back to Sanskrit. It means the blood in you and the blood in your family. "Blood is thicker than water" means that family is more important no matter who the person is. Kinship is a condition of sharing the blood of family in some way. Example; I don't know the person, I don't like the person but we share a common experience or goal or task which makes us work together and we have a kinship while working together. After many years we meet again and we know each other and we have that kinship. My kin is my family.

http://www.thefreedictionary.com/kinship

“Kinship" means the relationship between you and you parents, your sister, your brothers and so on. you and your parents are kinship. also with your sister, brothers, daughters, sons etc. In all, the relationship between you and your families is kinship.

Kinship is alike to friendship.