Coroners officers in Halifax are asking for help to find family members of a woman who died in Calderdale Royal Hospital on December 25.
Magdalena Jones Marmot was 40 when she died. Her death is not being treated as suspicious.
Coroners officers have spoken to her friends and found that she had family living in America.
It is also thought that Ms Marmot might have had a half sister, and coroners officers are particularly keen to trace her.
Ms Marmot was born in Islington, London, to a Daniele Broadway, who was born in France.
It is thought that Ms Broadway married a man called Timothy Coley in 1968 in St Pancras but possibly divorced in 1974.
The half-sister coroners officers are trying to trace is possibly living in the London area and called Sarah Coley.
Inquiries by the officers have also uncovered a daughter to Ms Broadway by the name of Thumper Jones Coley, born in Sheffield in 1969.
One line of inquiry is that Thumper changed her name to Sarah.
Anyone who can help is asked to call the coroners officers on 01422 354606.