Original: Their maternal grandfather was Numitor, rightful king of Alba Longa, a descendant of the Trojan prince, Aeneas and father to Rhea Silvia (also known as Ilia).
Simplified: Rhea Silvia was the daughter of Numitor Silvius, king of Alba Longa, a legendary town founded by Ascanius, son of Aeneas, prince of Troy.