Unlike nouns which are large classes of words which are constantly evolving, pronouns are a small and static class of word. There are around 60 in everyday use in English. However, because there is a cultural dimension to pronoun use, usage does change to reflect political and cultural changes. There are six types of pronoun:
Personal, possessive & reflexive pronouns
Personal pronouns, possessive pronouns and reflexive pronouns are closely related. Personal pronouns inflect in the 1st and 3rd persons when used as complements, direct and indirect objects, and in prepositional phrases. Reflexive and possessive pronouns are invariable.
Impersonal pronouns
Impersonal pronouns are concerned with sets and populations considered from a neutral perspective. There are two sets. The first set might be called true impersonal pronouns.
The more emphatic forms whosoever, whomsoever and whatsoever are less commonly used today.
The second set are effectively adjectives that have become detached from an accompanying noun. This may just be a case of elision. For example, few have the choice may just be a shorter way of saying few people have the choice.
Interrogative pronouns
Interrogative pronouns are used to pose questions to which the answer is a person or thing. The longer form is used to convey uncertainty or surprise: whatever can that be?
These pronouns are dealt with together with interrogative adjectives and adverbs in the entry covering Questions & Relative Terms. https://www.language-cafe.org/?p=581
Relative pronouns
Relative pronouns are used to head a relative clause. They replace an antecedent in another clause to which they refer.
Note that in a relative clause, which and that refer to antecedent things, whereas in questions what refers to things. This is because relative clauses are an alternative to the use of adjectives to qualify or provide additional information. For that reason, whatever and whatsoever can be used as relative pronouns because they have the force of adjectives, as in, for example: whatever book it is, or whatsoever reason is given.
These pronouns are dealt with together with relative adjectives and adverbs in the entry covering Questions & Relative Terms. https://www.language-cafe.org/?p=581