Is this a possibility?

Cacran

The issue is:-
Daughter and partner split. They have joint mortgage.
She doesn't earn enough to take over the full mortgage.
He does but does not want to live in the house.
Could her brother take over the partners mortgage, leaving it in both our daughter and son's name.
How difficult/possible would that be?

kingstreet

A 'one-off, one-on' transfer of equity may be possible.

Some lenders would require a new mortgage to replace the existing one. Legal work would require a solicitor to handle the transfer and new mortgage deed.