"each" and "neither" are properly or traditionally grammatically singular. "their" in #1 can be construed as singular "their" -- used, presumably, because the people involved are of mixed or unknown ***. "his or her opinion" would be formally correct (and in my opinion preferable in careful English), but in practice singular "they" is common in such cases.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
taruns1008Can you please give some more example where sentences have use both "their" and "his/her" to illustrate that, so I can understand the concept in better way?You will find plenty of examples at https://en.wikipedia.org/wiki/Singular_they