AnonymousPlease advise re the cat which belongs to Grace. Because Grace ends with an /s/ sound I wonder if it Is Grace's cat? Or Grace' cat?
I agree with Yankee. Yet, it must be said that there is a tendency among today's grammarians to standardize the often entangled genitive of English. That may deprive English of some of its most fascinating ways to denote possession. This charming jumble wouldn't be there if a Language Academy had had its say about it a few centuries ago. Here are a few examples from Otto Jespersen's Essentials of English Grammar:
"Note especially for conscience' sake, for goodness' sake (on account of the following s); before sake the s is also sometimes left out, even if the word does not in itself end in s: for brevity sake, for fashion sake."
CB