Depending on where OP is, that’s not strictly true. If you are in a situation such as this, at least within the UK, you are not strictly entitled to the rights of a tenant if you do not pay rent nor do anything in lieu of rent.
Basically in the UK if you do not have a tenancy agreement, cohabitation agreement, or license to occupy, then it can start getting very complicated. If they were named as a property owner, or had a common understanding of financial interest in the property, they might be able to fight for a stake of the house, but that isn’t really the point here. In the end whether they can be kicked out legally is a complex issue (at least in the UK) and not really a question we could answer here.