cohabitant
/kəʊˈhæb.ɪtənt/Definitions
1. noun
a person who lives with another person, especially in a marriage or a romantic relationship, but is not married to them
“After the breakup, Sarah remained the cohabitant of their shared apartment.”
2. noun
a person who shares a living space with others, often in a communal or group setting
“The cohabitant of the commune helped with the daily chores.”