Saint David of Wales was born to the Welsh royalty, the son of King Sandde, Prince of Powys, and of Saint Non. It is unknown if he had any siblings. He neither married nor fathered any children.
If Lucy had any siblings there is no record of them.
If Matthew had any siblings I can find no reference to them.
If Valentine of Rome had any siblings there is no record of them.
There is no historical record of Saint Monica having any siblings. She is mainly known for being the mother of Saint Augustine and for her strong faith and devotion.
There is no mention in any biographies about any possible siblings of Patrick.
Historical records are unclear about Saint Cecilia's siblings. Some sources suggest she had brothers, while others do not mention any siblings. The focus is often on her life as a martyr and patron saint of musicians.
Yes, Saint Sophia had three daughters named Faith, Hope, and Charity, but she did not have any siblings mentioned in historical records.
Saint Lucy is believed to have had three siblings.
There is no record of Saint Barnabas having siblings in the Bible or other historical texts.
There is no definitive information about Saint Genevieve having any siblings. She is commonly believed to have been an only child.
Saint David of Wales was never married and had no children.