Seafield House in Ayr was built in 1888 by Sir William Arrol, who designed the Tay Bridge, Forth Bridge and Tower Bridge in London, but has fallen into disrepair and has only recently been saved from demolition.
Now two Arrol family members are supporting the newly-launched Friends of Seafield House, who are calling on the site's owners NHS Ayrshire and Arran to carry out renovations.
The group has also received high-profile backing from conservationists SAVE Britain's Heritage, while Patrick Lorimer, Director of ARPL Architects, has stepped forward to spearhead the campaign.
Seafield House became a children's hospital after it passed out of the family's hands, but since it was boarded up in 2005 it has lain unused and is roofless after it was badly damaged in a fire four years ago.
Sir William's descendant Andrew Arrol, who as surveyor to York Minster is in charge of one of the most important and ambitious repair and restoration programmes in the British Isles, has become the group's patron alongside his distant relative Kirsty Menzies, who has joined as a founding friend.
Mr Arrol said: "In my view Seafield House can certainly be saved. It is very well built of good durable materials and potentially has many years of life ahead of it."
The campaign group was officially launched last week at a meeting and site visit to the derelict building. Campaigners are calling for an urgent programme of works to stop further deterioration during the coming winter.