The correct and agreed locution is "family members" and "frontier workers" (19 Mar Draft, PART TWO, CITIZENS' RIGHTS, TITLE I, GENERAL PROVISIONS, Article 8, Definitions (a) and (b) respectively, p 8)

Gibraltar Chronicle | Withdrawal agreement `protects cross-border passage', Lords told
"Lord Callanan, Minister of State at the Department for Exiting the European Union, was responding to a question from the Liberal Democrat peer Lord Jones of Cheltenham, who had asked what arrangements the UK Government would introduce to 'deal with the border' after Brexit."

Diversity is the key to economic and political evolution.