As NJ says, it doesn't look like a sublet. A sublet involves the lessee vacating the property , or part of it, entirely and exclusively, to the benefit of another as a tenant. If I invite my elderly mother to stay, without reward, in my house , I am not subletting. She would only be a licensee at best; she is my guest. If she was a paying guest; I was using the property as a boarding house; I still wouldn't be subletting ,though I might well be in breach of another condition , that of not conducting any trade or business or suffering the premises to be used for the purpose of a business, but that's another matter.
A solicitor is needed to establish the facts and the degree to which this may fall within subletting.