Yes it is the proper English way to write it
Sister-in-law
Answer:
Use an apostrophe in the possessive form of a noun to indicate ownership. To
show
ownership, add apostrophe + s to the end of a word, with one exception: To show
ownership with a plural noun already ending in s add only the apostrophe.
All singular nouns show possession by adding apostrophe + s ('s), including those
that already end in s.
Examples:
A boy's shirt is under the chair.
The child's toy was on the shelf.
Lois's book is fascinating.
The bus's door was still open
B homophone a homophone is a word spelled differently but sound the same
