Clarification on clan formation?


### On what basis were the clans formed in naruto?

The blood siblings Indra and Ashura are from different clans (Uchiha & Senju
respectively)., whereas other siblings, e.g. Itachi and Sasuke are from the
same clan (Uchiha).

The first shinobi who got chakra was Kaguya. So, technically whoever posesses
chakra should've inherited it from her. In that case, all should be from the
same clan.

Now, here's my long time doubt. How is it decided that Naruto is from the
Uzumaki clan when his father is from the Namikaze family and has no clan?

Is a person's clan decided based on the abilities of the person? If yes, how
is their ability evaluated right after they are born?




As a competing answer to the one of
[@MadaraUchiha](https://anime.stackexchange.com/a/11336/1751), here's my take.

The clan belonging is solved quite easily. The clan-belonging is given through
the generations maternally.

This means what decides the clan is not the father, but the **mother**. In
Naruto's case that is Kushina Uzumaki

Other than that, the [naruto-wiki](http://naruto.wikia.com/wiki/Clans) gives
some nice information:

> A clan (一族, Ichizoku; **Literally meaning "family"** ), in the loosest sense
> of the term, refers to a family or group of shinobi who form a basic unit of
> a shinobi village. Majority of these clans were **mercenary military
> forces** even before the First Shinobi World War. [...] Membership in a clan
> is usually determined by **blood relations and genetics** , which is vital
> in the usage of kekkei genkai and secret techniques. [...] While clans **may
> be composed of many individuals** and extended families, many clans
> mentioned and seen in the series were somewhat **limited to a nuclear
> family.** Highlighting by me

It seems that the most clans seen, are just the mentioned nuclear families.
This leads to the assumption, that one line of family that somewhen declared
itself a clan **is** a clan. Some family lines had more offspring, and some
had less. for example the Hyuuga-clan has multiple branch families, who are
subordinate to the main family. The Uchiha clan on the other hand seems to
just be loosely organized.

Some clans seem to have a definitive familiy head (Hyuuga, Akimichi, Nara).
Other clans are not organized (Uchiha, Uzumaki, Inuzuka, [...]).

Clans mostly differ in chakra affinity and Kekkei Genkai, as well as battle
style. In fact that seems to be the only thing shared in a clan. This Chakra
affinity seems to be genetic, so that you are rather born into a clan than
"join" it. It seems that not every person has his / her own clan, most
prominent examples are probably [Kakashi
Hatake](http://naruto.wikia.com/wiki/Kakashi) and [Might
Guy](http://naruto.wikia.com/wiki/Gai).

