In February, Facebook expanded the gender options available for trans and gender-nonconforming users to list on their profile. Building on that success and addressing a remaining complaint, the site quietly rolled out the ability to designate family members using nonbinary and gender-neutral terms recently.
In addition to being able to list family member using terms like "father," "mother," "brother," "sister," "aunt," and "uncle," the latest update allows users to designate their relationship to other users using terms like "sibling (gender neutral)," "child (gender neutral)," "cousin (gender neutral)," and "sibling-in-law (gender neutral)."
Unlike February's update, which came with an official announcement from Facebook's diversity page, the company did not issue a public statement on the new relationship options, resulting in far less fanfare. It appears that not all users in the United States yet have access to these new options, and it is unclear whether these are here to stay or merely part of the social networking site's periodic tests.