Complex sentence: After the incidents of the film, Steven moved from Long Island back into his birthplace of New York City, where he attended the Professional Children's School with the Culkin brothers, who would go on to portray the Martini brothers on film.
Split into simpler sentences: After the incidents of the film, Steven moved from Long Island back into his birthplace of New York City, where he attended the Professional Children's School. There, he met the Culkin brothers, who would go on to portray the Martini brothers on film.