And for some cause, Sugriva, driven out by his brother, for a long time dwelt with me at the Hrisyamukh. And it came to pass that the mighty son of Dasaratha the heroic Rama, who is Vishnu’s self in the shape of a human being, took his birth in this world. And in company with his queen and brother, taking his bow, that foremost of bowmen with the view of compassing his father’s welfare, began to reside in the Dandaka forest.

In plain words: Hanuman says Sugriva was driven out by his brother and lived with him. In that time Rama was born, who is the god Vishnu in human form. Rama went to live in the Dandaka forest with his wife and brother to honor his father's word.