Firstly for inheritance of property and titles; Though Primogeniture (inheritance of the whole estate to the first born male or if no males the eldest female) was not a German custom, your parentage has to be clear and legitimate for you to have any customary or legal claim to any inheritance. For this reason, women must not have sex outside of marriage (it's fine for men as it does not create legal or customary inheritance issues), if they did, parentage would be unclear and it would create uncertainty. Uncertainty creates opportunity for "contests" to take place and there are all manner of greedy relatives and grasping overlords just waiting for the chance to take someone's inheritance. Here particularly kinship can be a liability, if a potential successor's legitimacy was in doubt or the main family line died without heir, a whole slew of contenders might be able to stake a claim, drawing in their allies and other kin. For all that, bastard sons did get inheritances from their fathers (lucky thing for the sons of churchmen), as they are kin and that matters a lot.
Secondly and more importantly, kinship counts for mutual aid, protection and trust. If an individual falls upon hard times their family will likely aid them, both from feelings of affection and through social obligation. This was especially important if someone has to deal with a new land or locality where they do not have a network of friends and contacts and might lack appropriate ability to access local entitlements. Here kin provides a link and a safe point for aid and introduction to a new social world, as well as a place to stay until you get a something of your own. Of course, the utility of this varies according to how far afield you kin tend to be spread, but it's fair to say that kin networks go where they were needed. This was afterall a key motive for colonisation by traders and political marriages amongst nobles. If injury or even death were the type of misfortune that befell a person, kin are still able to "help" after the fact, by providing systematic revenge, never harm someone with strong and violent kinsfolk.
Lastly and most elementally, kinship provides a clear guide to identity and belonging. It is relatively simple stable and obvious. It provides a way to simply order the world in relation to yourself. People will give a reputation, character and personality to your kinship group and that will inevitably colour how they see you as a member of it. If you don't have goals of your own, take on your father's goals, your uncle's goals or the goals of your noble house. Even if you do have goals of your own, tough, there is considerable social and familial pressure to work in your families interests. However, kinship is really a genuine plus, individuals can choose to ignore any obligations and all they usually really risk is social disapproval and gossip.