When is it inappropriate to use the pluralizing suffixes -たち, -ら?

Question

In "A Dictionary of Advanced Japanese Grammar", it says that there are cases where -tachi cannot be attached to a noun, as in:

a. 川本と柴田は大学の教師(*たち)だ。(Kawamoto and Shibata are college professors.)

b. 彼には子供(*たち)がある。(He has a child/children.)

"Except in the above cases, the attachment of the suffix -tachi is optional."

I assume that the use of -tachi in (a) is improper because the plural is evident as is, but why is (b) the case? Is there a nuance to Japanese pluralizing suffixes apart from just making a noun explicitly plural?

Answer 1

I think the reason たち cannot be used in those sentences is that the words before it don’t refer to concrete people.

川本と柴田は大学の教師だ。
Kawamoto and Shibata are college professors.

川本 and 柴田 are concrete people, of course, but 教師 refers to their status, not Kawamoto and Shibata themselves. It is an abstract concept.

彼には子供がある。
He has a child/children.

子供 in this sentence is also an abstract concept that refers to someone to whom you are a parent, not any concrete child or children.

The following sentence gets a different meaning.

彼には子供たちがいる。
He has his children (to take care of, count on, etc.).

子供たち here is understood as referring to his own children, or children under his care.

This concreteness becomes more obvious when たち follows a proper name.

太郎たちはまだ来ていない。
Taro and others haven’t come yet.

In this case, たち plays a similar function to “et al.”

Maybe you should stop seeing it as a “pluralizing suffix” and start seeing it as a marker that extends what it marks (e.g. 子供) into a larger group of people that includes it.