Possessive apostrophe for owner of owner of owner of

I've read Preferred way to apostrophise in case of dual or multiple ownership by distinct entities and "Nikki's and Alice's X" vs. "Nikki and Alice's X", but my question is a little different. Not sure if the title is correctly chosen or not.

So the question is, if something belongs to a person, whose name I don't know for example, then I would say:

1. It's my uncle's sister's nephew's object
2. It's my uncle sister nephew's object

I suppose the first one would be correct, but it looks strange. Can anyone point to a rule that specifically states how to deal with the possessive apostrophe in those situations?

The first example is the correct usage as it is the object of the nephew of your uncle's sister.

1. It's my uncle's sister's nephew's object

It does not matter how many people are in the list, each one will still have a possessive apostrophe in a list like this.

1. It's my uncle sister nephew's object

This doesn't make any sense as it describes the object of someone who is your uncle-sister-nephew.