A UK government policy paper, published on 4 April 2019, has established that UK nationals returning from the EU to the UK after Brexit can be joined by their EU or non-EU national family members, whether the UK leaves the EU with or without a ratified withdrawal agreement.
The deadlines for family reunification for returning UK nationals depends on when the relationship started.
Relationships beginning before Brexit
A spouse or partner and other existing close family members (such as parents, grandparents and children), where the relationship existed on exit day (or where a child was born overseas after this date) will be able to join a returning UK national in the UK and apply to the EU Settlement Scheme until the end of March 2022, after which they will have to apply through UK Immigration Rules.
Relationships beginning after Brexit
A spouse or partner and other dependent relatives will be able to join a returning UK national in the UK and apply to the EU Settlement Scheme until 31 December 2020, after which they will have to apply through UK Immigration Rules.
Children born after Brexit will continue to have the right to British citizenship, wherever they were born.