Hello Sherylle my name is ***** ***** I will help you with this.
Has there been a succession to the tenancy before please?
Only one person is allowed to succeed to a regulated tenancy. Joint succession is not allowed. A regulated tenancy can be passed to a husband, wife, civil partner or someone else living with the tenant when the tenant dies. The tenancy remains a regulated tenancy if it is is inherited by the husband, wife, civil partner or someone else and no one else has previously inherited the tenancy.
But if it has been succeeded once, sadly it can not be again. That means that your sister would have to move out, once the Landlord finds out.
I am sorry if this is not the answer you want and certainly not the one I want to give you, but I have a duty to be honest.
Can I clarify anything for you about this today please?
Sadly you are only entitled to ONE succession and there is no time limit.
It passed from your Dad to Mum. I am sorry.