Plural possessives

We never place an apostrophe for the possessive in the first word -- 'sisters' for example -- but we place an 'apostrophe s' in the second word, 'law.'

Are these plural possessives (in boldface) correct? Thanks.

sisters-in-law's business
(More than one sister-in-law owns the business)
brothers-in-law's business

(More than one sister-in-law owns the business)
sons-in-law's industry
(More than one son-in-law is involved in the industry)
presidents-elect's offices
[The presidents-elect's offices are currently busy at the moment.]
more than one president-elect's ownership
attorneys general's office or offices
[All of the attorneys general's responsibities included ...]
more than one attorney general's ownership
surgeons general's office or offices
[All surgeons general's equipment will be seized by the government.]
more than one surgeon general's ownership
poets laureate's work or works
[The Indiana Arts Commission hosted the poets laureate's "Sporting Words" conference with the help of grants.]
more than one poet laureate's ownership
heirs apparent's inheritance or inheritances
[One heir apparent = heir apparent's title; more than one heir apparent = heirs apparent's title.]
more than one heir apparent's ownership
editors-in-chief's responsibility or responsibilities
[The editors-in-chief's primary responsibilities are to oversee the entire operation.]
more than one editor-in-chief's ownership