The photographs of Nora Dorricott, who died in 1956 aged 39, went missing when Trish Dorricott's Fiat Abarth 500 was stolen from outside the Premier Inn at Bentley Green, Walsall, last month.
Miss Dorricott had travelled to Walsall to show the photographs to Paul Bennett, whose great uncle Gordon "Dusty" Bennett had been married to Nora before he was killed in the Spanish Civil War.
The distinctive yellow car, decorated with butterfly decals, was later recovered by police, but the photographs were gone.
Miss Dorricott said her mother married Dusty when she was aged about 18, but Dusty was shot dead while fighting against General Francisco Franco's forces at Gandesa in 1938. Nora later remarried Miss Dorricott's father.
She contacted Paul Bennett after reading about his story in the Express & Star.
Miss Dorricott, who is 79, said she was prepared to offer a reward for the return of the pictures.
"The photographs meant far more to me than the car," she said.
Dusty, who was born in George Street, Walsall, in 1907, had married Nora in the mid-1930s before joining his older brother Don to fight against Franco's fascist regime in 1938.
Dusty was killed when Don, a machine gunner, was spraying bullets towards Franco’s fighters, who by this time were in the ascendancy.
The plate on Don’s gun slipped, so he couldn’t see over the sights, and Dusty, who had been feeding the ammunition belt into the gun, stood up to replace the plate. He was struck in the chest by an enemy bullet and instantly killed. Having ensured his brother was dead, Don removed Dusty’s personal belongings, and made a makeshift grave by pulling the wall over his brother’s body.
His widow Nora later married Miss Dorricott's father.
Don, who died in 1974, never knew what became of this brother's body. But the Express & Star revealed in October that, thanks to DNA technology, Don's grandson Paul could finally discover the details of Dusty's final resting place.
Paul, a retired social care worker from Walsall, was contacted by the Spanish Government last year asking for a sample of his DNA in an attempt to identify a body found in a mass grave close to where Dusty died. The body was wearing a gold ring bearing a hallmark from the Birmingham assay office, dated 1910.
The Spanish authorities contacted Birmingham Council, whose records showed that only two fighters from the West Midlands were killed in that region: one lived in Birmingham, the other was Dusty.
Paul said: “I’ve spent a lifetime searching to find what happened to him. Hopefully it will be the closure of a chapter which haunted my grandad his whole life.”
After reading the story, Miss Dorricott, who grew up in Walsall but now lives in Northampton, contacted the Express & Star, and arranged to meet Paul to show him the photographs.
Miss Dorricott said the photographs were in a blue folder.
The car was stolen sometime between 10pm on April 5 and 2am on April 6.
West Midlands Police said the car was recovered, but no photographs were found in it.
Anybody with any information regarding the whereabouts of the photographs can contact Mark Andrews at the Express & Star on 01952 241491.