Complex sentence: In 1919 twin brothers Michael and Lance Gallant were born in New York City, a pair so alike, even to a T-shaped birthmark on their left wrists, that even their mother could not distinguish between them.
Split into simpler sentences: In 1919 twin brothers Michael and Lance Gallant were born in New York City. They were so alike, even to a T-shaped birthmark on their left wrists, that even their mother could not distinguish between them.