which for people, never possible?

[keannu]

Is "which" not possible to use for people as in the following?
My grammar book defines "which" is for animals or things, but I've seen a writing where they used it.

ex)1)There are two guys. One of which is really scary.
2) I have two sisters which are all tall.

 

[allenman]

That is correct.
1) would use "of whom"
2) would use "who"

 

[probus]

Which for people is not only possible but common and often best.

See the thread "who of you", although that thread perhaps did not convey sufficiently clearly that "which of you" is the most common and best usage.

 

[Rover_KE]

1)There are two guys, one of whom is really scary.
2) I have two sisters who are both tall.

Rover