Birth of Baali and sugreev
How these two brothers were born is an interesting story. On the peak of Sumeru Parvat there is Brahmaa's court - in 100 yogna wide area. Once Brahmaa Jee was doing Tapasyaa, two drops of tears fell from His eyes. Brahmaa Jee took them in His hand wiped His hand with His body. Later when He shook His hand one drop fell on the ground. A Vaanar was born from that drop. He said to Vaanar - "You stay on the peak of this mountain. After some time it will be good to you."
The Vaanar went away and started living there on fruits and flowers. He used to offer flowers to Brahmaa Jee daily. Thus a long time passed. One day Riksh Raaj got thirsty so he looked for a pond, and as he bent down to drink water, he saw his shadow in that water. He thought "Who is this my enemy here? I will kill him." And he jumped into the water. But when he came out he found himself changed into a beautiful woman.
By chance both Soorya and Indra were passing from there. Both saw that beautiful woman, and had a desire to have her. Indra's semen got ejaculated and fell on the head of the woman, so a Vaanar was born from that. Because he was born from her hair, he was called Baali (Baal means hair in Hindi); while Sun's semen got ejaculated and fell on her neck, so another Vaanar was born from there and was called Sugreev (Su means good, and Greev means neck in Hindi).
Indra gave a qualitative gold necklace to Baali and Soorya appointed Hanumaan in the service of Sugreev. After this that woman again became Riksh Raaj. Thus Riksh Raaj was both their mother as well as mortal father. After some time Riksh Raaj went to Brahmaa Jee. Brahmaa Jee asked him to live in Kishkindhaa Nagaree and sent a messenger with him to appoint his elder son as the king of that Nagaree. Vaanar were already living there. So all started living there. Baali was appointed the king of Vaanar. After some time Riksh Raaj died.