Agreement is on the bases of a two-term "gender" system, personal and non-personal:
The girl, who… The ground, which…
The men of towns who… The sheep-bell, which…
The farmer who… The sunlight, which…
One who… The time of life at which…

It will be seen from these examples that "personality" is ascribed basically to human beings but extends to creatures in the supernatural world (angels, elves, etc.) which are thought of as having human characteristics such as speech. It does not extend to the body or character, in part or whole, of a human being, living or dead, when this is considered as separate from the entire person. Their owners can regard pet animals as "personal", at least. On the other hand human babies can be regarded as not having developed personality.

Case in the relative pronoun
Case is used to indicate the status of the relative pronoun in its clause. There are two situations to consider:
1) If the pronoun is in a genitive relation to a noun head, the pronoun can have the form "whose". "Whose" is a relative possessive word, used as a determiner before nouns in the same way as his, her, its or their. It can refer back to people or things. In a relative clause, whose + noun can be the subject, the object of a verb or the object of a preposition. "Whose" can be used in both defining and non-defining clauses.
Eg: Oak was seized with a misgiving as to whose ear was the recipient of his answer.
… he was stealthily turning to discover, if possible, into whose hands he had fallen.

2) With a personal antecedent, the relative pronoun can show the distinction between "who" and "whom", depending on its role as subject of the relative clause or as object or as prepositional complement:
Eg: …all men of the stamp to whom labour suggests nothing worse than a wrestle…
When the governing preposition precedes its complement the choice of "whom" is obligatory. When it does not, or when the relative pronoun is the object, there is some choice between "who" or "whom".

Relative pronoun and adverbial
The functions and interrelations of the relative pronouns are best handled in connection with relative clauses and nominal relative clauses.  The "wh-" series reflects the gender (personal/non-personal) of the antecedent:
Personal: who, whom, whose
Non-personal: which, whose
There is an inflected genitive for both "who" and "which", but there is a preference for the of-genitive with non-personal antecedents. Instead of "whose", we can use "of which" or "that…of" to refer to things, and these are sometimes preferred. The personal objective "whom" is often replaced by "who" but never when preceded by a preposition. "Who" can be used as an object in defining clauses in an informal style. "Whom" is more formal.