When to read 一人 and 二人 as いちにん and ににん?

Question

WWWJDIC lists いちにん and ににん as alternative readings of 一人 {ひとり} and 二人 {ふたり}, but I can't recall anywhere I heard those readings except when counting more than 10 people for example 三十一人 {さんじゅういちにん}. Is that the only situation where 一人 and 二人 are read as いちにん and ににん, or are there any other situations?

Answer 1

Other than your example 三十一人, I can think of 一人前, 二人前, 二人三脚, 二人羽織. But by itself, I don't think they are read as 'いちにん' or 'ににん'.

Answer 2

The only thing I can think of is 一人称【いちにんしょう】 and 二人称【ににんしょう】 meaning "first person" and "second person" respectively. This means "person" as in "point-of-view" or parts of speech ("third person" is 三人称【さんにんしょう】).