Hyphens and apostrophes:
"Mary is now in her mid-60s and fondly remembers her happy youth in the '50s."
"John is a well-known writer in his community."
However: "John is a writer and well known in his community."
"Greg was a high-risk high school student in the 1970s."
"The inspector made on-site visits to the new housing development."
"My three brothers-in-law's jointly owned house is spectacular."
The personal pronouns, yours, his, hers, ours, its, theirs, and whose, do not require an apostrophe; it's, a contraction, means "it is" and who's, likewise, a contraction, means "who is."
"The toys in the box belong to my brother's friend's cousin." [one brother, one friend]
"The toys in the box belong to my brothers' friends' cousin." [more than one brother, more than one friend; If there's some ambiguity as to who's who, I'll let you, the reader, sort that out! Oh, well, here I go: My brothers John and Fred have friends named Eric and Bob, whose cousin Gary owns the toys in the box.]
Enuf!
CoCo