Conversation so far:
Where was George M. Cohan's birth day written?
A baptismal certificate indicated that he was born on July 3, but George M. Cohan and his family insisted that he was born Fourth of July!“
Where is George M. Cohan's birth certificate from?
A baptismal certificate was from St. Joseph's Roman Catholic Church.
Where was George M. Cohan born?
George M. Cohan was born in Providence, to Irish Catholic parents.
What state was George M. Cohan born in?
George M. Cohan was born in 1878 in Providence, Rhode Island.
What year was George M. Cohan born in?
George M. Cohan was born in 1878.
What was wrong on George M. Cohan's baptismal certificate?
The baptismal certificate had George M. Cohan's mother's first name incorrect.
What else did George M. Cohan's baptismal certificate say was wrong?
The baptismal certificate also had George M. Cohan's birthday incorrect according to the family.
What did George M. Cohan and his family say this erroneous information?
George M. Cohan's and his family always insisted that George had been born on the Fourth of July!“

Question: What did his parents do?
Self-contained rewrite: What did George M. Cohan's parents do?