Complex sentence: Coolidge's favorite pet, he was acquired by Grace Coolidge in 1922 after she became enamored with collies after seeing one of the breed perform in a circus, and later lived with the family in the White House.
Split into simpler sentences: Coolidge's favorite pet, he was acquired by Grace Coolidge in 1922 after she became enamored with collies, having seen one of the breed perform in a circus. He later lived with the family in the White House.