It hit me when I was editing this question which had the pronouns tag. I wasn't sure if 「娘」 is considered a pronoun in Japanese. Looking for relevant examples of kinship terminology in English, I think all the comparable terms I can think of are not categorized as pronouns. Wikipedia's pronoun page has this claim:
In English, kin terms like "mother," "uncle," "cousin" are a distinct word class from pronouns
This appears corroborated by dictionaries.
Wikipedia's Japanese pronouns page doesn't list such terms. There's no 母さん, 父上, 爺ちゃん, お姉ちゃん, or 兄貴. Another reference: 代名詞. So are they not pronouns? Why?