One-year-old Willow started nurturing the Flintstones-named trio Pebbles, Bamm-Bamm and Barney after their mothers rejected them.
Farmer Mandy Ellison watched in despair as the lambs were all shunned by their mothers because they were the weakest of their new offspring.
But she was amazed after placing Pebbles – the sickliest of the newborns – in Willow’s basket in front of the farmhouse fire.
The dog had been in the yard but ventured inside and snuggled up in the basket and curled herself protectively around the sickly lamb.
That prompted Mrs Ellison to add two other rejected lambs to the basket and now the family of four have become inseparable.
But the loving dog also finds time to protectively follow Mandy’s youngest son Mark, six, who has cystic fibrosis, around the farm.
Mrs Ellison, 42, said: “Some of the ewes have had triplets this year. When there’s that many, the ewes sometimes can’t cope so they reject them.
“The first one to be rejected was really poorly – she was rejected completely. She was still wet from being born and she was so cold that we honestly thought she was going to die.”
Taking pity on the little newborn, Mrs Ellison named her Pebbles and took her inside the family home where she lives with her husband, 38-year-old James, eight-year-old Coen, Mark and Willow.
She added: “We brought Pebbles in the house where we have a log burner and put her in the dog bed in front of the open fire and the Dalmatian got in and started licking her. I’ve never heard of it before – it was just an accident in all honesty.
“We just put the lamb in the dog bed to keep warm.”
When another two lambs were also rejected by their mothers, Mandy was even more amazed to see Willow’s caring nature was extended to them too.
Mrs Ellison, of Stockton-on-Tees, County Durham, added: “She’s never had puppies before in her life, but now she’s mothering these lambs like it’s going out of fashion. I don’t know that any other dog would do…