An Indo-European-like trait that Dairwueh and Sargaĺk share (but that Bryatesle lacks!) is case congruence on adjectives. What makes this particularly Indo-European-like (and not, e.g. Baltic-Finnic like or Kayardild-like) is the existence of distinct sets of morphemes for the adjectives and for the nouns.
I have understood that the origin for this in Indo-European is that morphemes originally used with pronouns for some reason migrated onto the adjectives, although this of course leaves open the question of the origin of the distinct morphemes on the pronouns. (However, typologically I doubt whether that's very unusual. We find small examples of similar things elsewhere, such as the Finnish -t accusative for personal pronouns, or the comitative requiring possessive suffixes on the noun - the latter possibly leading, over time, to a situation where the noun and adjective have distinct forms.)
What's this to do with names? In Dairwueh, personal given names can behave both like nouns and like adjectives, depending on the presence of a clan name. A patronymic can behave like a noun if no other part of the name is present.
would be the noun-like forms, and if Doras' father was Elti, you get
nom: Eltikar Doras
acc: Eltikan Doranna
dat: Eltikarz Doraar
gen: Eltikarz Doraat
loc: Eltikari Doraŋa
however, if a clan-name was involved, Doras too would - except in the nominative - inflect by an adjectival paradigm:
nom: (Eltikar) Doras Marzi
acc: (Eltikan) Doran Marzinna
dat: (Eltikarz) Dorarz Marziar
gen: (Eltikarz) Dorarz Marziat
loc: (Eltikari) Dorari Marziŋa
In the nominative, the patronymic has its own feminine form e.g. Eltikama (derived from the father's name, though), but in all other forms, it basically used feminine congruence instead on the masculine patronymic stem.
Nick-names of course exist, and tend not to adhere to this pattern. However, a nick-name nearly never is used in apposition with patronymics or clan-names.
As linguistic history goes by, other forms of 'family names' besides clan-names start appearing, with the usual suspects: professions, places of origin, remarkable attributes, etc.
// TODO: I should definitely finally get around to getting those adjective case markers done for Dairwueh.