Possessive pronouns do not have apostrophes
"It's" means "it is". If you mean "belonging to it", try "its".

"Who's" means "who is". If you mean "belonging to whom", try "whose".
(Vice Admiral Sir Charles Cockbrush KCB MBE DSO, who is finding it increasingly difficult to log into b3ta.com wants to duck your aunt and kick your puppy, Fri 31 Jul 2009, 16:45, 3 replies, latest was 15 years ago)

It's easier
if you list all the examples of possessive pronouns, then it is much clearer

whose?
(mine)
yours
its
his
hers
ours
theirs

Although, I have seen people write the possessive as their's, our's and even hi's

Ban the apostrophe for all genitives! It is an artificial invention anywho.
( Sextant goes to him is emotionally erect, on this day, Sun 2 Aug 2009, 3:43, Reply)

'It's' is the only one I keep getting caught out by,
that and plural possessives that end in an "S" *head explodes*
(theSHALROTH Gaga's tits are on fucking fire!!!, Mon 3 Aug 2009, 23:54, Reply)

You mean things like "women's clothes"?
Simples.

Add 's to a noun to get the possessive, unless it already ends in an S.

Boy - boy's
Boys - boys'
Girl - girl's
Girls - girls'
Child - child's
Children - children's
Man - man's
Men - men's
Woman - woman's
Women - women's
Person - person's
People - people's

There's no such word as womens, so womens' can't exist either.
(Vice Admiral Sir Charles Cockbrush KCB MBE DSO, who is finding it increasingly difficult to log into b3ta.com wants to duck your aunt and kick your puppy, Tue 4 Aug 2009, 15:15, Reply)