Kekkei genkai are considered abilities passed on through bloodlines, from this question: How is a technique characterized as a kekkei genkai? When discussing kekkei genkai, however, people never seem to include clan abilities such as the Nara shadow possession or the Inuzuka collaborative jutsu with their dog partners. Would these (or similar) abilities count as kekkei genkai, and if not, why not?
Nope, they are not. The abilities that you mentioned are just hiden (秘伝, not to be confused with "hidden") techniques, exclusive to a specific clan. There is a difference between them and kekkei genkai abilities.
Kekkei Genkai is passed down genetically, so every member of a clan has an aptitude for it. The hiden techniques, on the contrary, are not passed down genetically, but rather "taught", so in fact anyone could learn them if they were not kept in secret.
For example, take Parasitic Destruction Insect Technique, which is exclusive to Aburame clan. However, it's not a genetically-passed ability, it's rather that only Aburame clan knows what needs to be done in order to place the insects into one's body and to learn how to live in symbiosis with them.
You can read more on the subject here.
Also the ability to use a Kekkei genkai is affected by the chakra type you are born with, normally a shinobi is born with a single chakra type hiwever in the case of a Kekkei genkai user, the shinobi is born with two nature types