Adult Social Care Glossary, v 0.6

People who aren’t your family of origin, but who support you as family

A term used to describe people who are not related by birth or marriage yet whose bond is like that of family. Oftentimes LGBTQ+ people find and build their chosen family out of necessity, due to a lack of understanding or familial acceptance. [Definition of "Chosen family"; "Family of choice" is used in the accompanying article.]

Sometimes referred to as "Family of my own making". The Alzheimer's Society definition appears on their website in the context of LGBTQ+ people with dementia (under the heading "Relationships LGBTQ+ people with dementia may have" - click the heading to expand it). "Family of choice" or "Family of my own making" could presumably be applicable in other situations too.