Estate in Intestate , Appointing Administrator

[M123456]

I am trying to help my brother sort out the estate of Joint Owner of Property.

My brother has been joint owner of property where they both lived , but with no relationship between the two of them.
The property is owned as Joint Tenants.
The Other owner died in April and no will can be found, even had a Solicitor carry out a search. So the estate is Intestate.
As well as the house there is Investments but also credit card debits.

The other owner has a surviving sister in Canada who my bother has spoken too , she happy that he get to keep the house , but we cant get her to do any think about appointing some one to Administer the estate.
How do you get some one to Administer the Estate if nears relative want act.

[des8]

If there are no relatives willing to take on the task of administration of an intestate estate, it will pass to the government as bona vacantia. https://www.gov.uk/unclaimed-estates-bona-vacantia

As the house was owned with the deceased as "joint tenants" it automatically passed to him on the other's death.
To have it registered in his sole name I believe he only needs to write to Land Registry enclosing a copy of the death certificate