Conversation so far:
What year was Ralph Waldo Emerson born?
Ralph Waldo Emerson was in 1803.
Who was Ralph Waldo Emerson's father?
Ralph Waldo Emerson was son of the Rev. William Emerson, a Unitarian minister.

Question: Was he the only child of his parent?
Self-contained rewrite: Was Ralph Waldo Emerson the only child of his parent?