After explaining who vs. that, I realized I’m still getting hung up on who’s versus whose. I like apostrophes to show ownership. Unfortunately, with these two the one with the apostrophe does not equal ownership.
Who’s is who is. Or who has. It does not show ownership.
Examples: Who’s at the door? (Who is at the door?)
Who’s leave? (Who is leaving?)
Whose is for ownership.
Examples: Whose sandwich is this?
Whose children are those?
Make sense now?