This is a matter of choice for you. First, breaking a lease is not "illegal"; so there is no questions of "legally" or "illegally" breaking a lease. Most leases have provisions allowing for the termination of the lease in certain conditions. If your situtation is not covered, and you want to break the lease, then you are technically in breach of contract. You will then be liable for all damages to the tenant as a result of your breach. These may include higher rental costs (for the balance of the lease term), moving costs, attorneys fees and the like. You may want to consider discussing with them your need to have the home sooner...and your willingness to "buy them out" of the lease for a certain $ figure. If they do not want to move, then you are stuck with the option of keeping their lease and finding alternate accomodations for the family member...OR risking a suit where you are charged with breach of contract.