Complex sentence: Stephen's "Lesser Legend" adds that he was born in Esztergom, which implies that he was born after 972 because his father, Géza, Grand Prince of the Hungarians, chose Esztergom as royal residence around that year.
Split into simpler sentences: Stephen's "Lesser Legend" adds that he was born in Esztergom. His place of birth also implies that he was born after 972, because his father, Géza, Grand Prince of the Hungarians, chose Esztergom as royal residence around that year.