I signed a co-tenancy agreement in November, with one other person. In January, the other co-tenant starting having her boyfriend stay. He has since been here permanently, and she has provided him with a key, without my agreement or the agreement from the real estate agents (REA). I have tried to raise the issue with her, however she refuses to talk to me about it, to the point of getting me threatened. The boyfriend verbally agreed to assign my share of the lease to him, however they have since ignored the paperwork and done nothing about it. I have raised the issue with the REA, however they are referring to it as a tenant/tenant issue, which they're saying they can't play any part in. Legally, where do I stand under property law with breaking the lease / getting him removed from the property? My understanding is, that him being there is a breach of the residential tenancy agreement.