Ayodhya, (present-day Uttar Pradesh, India)
Dasharatha (Sanskrit: दशरथ, IAST: Daśaratha) was the king of Kosala kingdom and the descendent of Ikshavaku Dynasty and father of the Lord Rama. His capital was Ayodhya. Dasharatha was the son of Aja and Indumati. He had three main throne queens: Kausalya, Kaikeyi and Sumitra, and from these unions were born Rama, Bharata, Lakshmana and Shatrughna. He is mentioned Ramayana and Vishnu Purana.
King Dasharatha was an incarnation of Svayambhuva Manu, the son of the Hindu creator god, Brahma.
Dasharatha was the son of King Aja of Kosala and Indumati of Vidarbha. His birth name was Nemi, but he acquired the name Dasharatha as his chariot could move in all ten directions, fly, as well as come down to earth, and he could fight with ease in all of these directions.
Dasharatha became the king of Kosala after his father died. He was a great warrior who single-handedly conquered the whole earth with his prowess and defeated and slew many asuras in war.
According to Valmiki Ramayan's Ayodhya Kanda, Chapter 34, Verses 10 to 13, King Dashratha had around 350 wives,  among which 3 of them were his favored throne queens. Kausalya was Dasharatha's chief queen. Sumitra and Kaikeyi were other favored queen consorts. Kausalya was from the Kingdom of Dakshina Kosala, Sumitra was from Kashi, and Kaikeyi was from Kekeya Kingdom.
Dasharatha performed a yajña with the help of Sage Rishyasringa, an expert of Atharvaveda on the advice of Vasishtha.
The Yajña was the Putra-kameshti at the bank of Manorama river. Dasharatha and Kausalya had a daughter Shanta, who was Rishyashringa's wife. As the conclusion of the Yagna drew near, Agni sprang out from the Yagnakunda (sacrificial fire pit) and handed Dasharatha a pot of kheer (payasa), advising him to distribute it among his queens.
Kaushalya ate half the kheer, Sumitra ate a quarter of the kheer, and Kaikeyi ate some and passed the pot back to Sumitra, who consumed the kheer for the second time.
Thus, the queens conceived after the consumption of the kheer. Since Kausalya had consumed the largest portion, she gave birth to Rama. Kaikeyi gave birth to Bharata. Sumitra, who had consumed the kheer twice, gave birth to Lakshmana and Shatrughna. The part Sumitra took from Kausalya resulted in birth of Lakshmana, who was close to Rama. The part Sumitra took from Kaikeyi resulted in birth of Shatrughna, who was close to Bharata.
A maid of Queen Kaikeyi named Manthara convinced her that the throne of Maharaja Dasharatha belonged to her son Bharata, and that her stepson, crown prince Rama (the hero of the Ramayana)— should be exiled from the kingdom. The ugly maid also reminded her of the promise made to her by Dasharatha when she saved him in the great war against the asuras, that she was promised 2 boons and she could use them to make Bharata king. By crowning Rama as king, Dasharatha would be doing an injustice to her, as she wanted Bharata to be king.
Thus, after this conversation, Dasharatha was reminded by Kaikeyi about the two boons he had yet to fulfill for her. She talked of the time when she saved him from the demons during a celestial battle against Sambasura, an enemy of both Indra and Dasharatha. During a fierce battle between the two, the wheel of Dasharatha's chariot broke and Sambasura's arrow pierced the king's armor and lodged in his chest. Kaikeyi, who was acting as Dasharatha's charioteer, quickly repaired the broken wheel and then drove the chariot away from the battlefield. She nursed the wounded king back to health. Touched by her courage and timely service, Dasharatha offered her two boons. However, Kaikeyi chose to ask for those boons later, and King Dasharatha was obliged to fulfill them. Kaikeyi demanded that Bharata be crowned king and Rama be sent to the forest for fourteen years. Hearing this, Dasharatha fell into a swoon and passed the night in a pitiable condition in Kaikeyi's palace.
After Rama's departure to the forest, Dasharatha lay in his bed with a wailing Kaushalya. He suddenly remembered an incident which had occurred in his past. He narrated to Kaushalya about how, by accident, he had killed a young man named Shravana, mistaking him to be an elephant. Dasharatha, who was then a crown prince, had gone hunting on the banks of River Saryu. He was an expert in hunting by determining the direction of sound and heard the gurgle of an animal drinking water. Mistaking it to be water flowing through the trunk of an elephant, Dasharatha shot an arrow. He became mortified when he heard a human cry as the arrow found its target. Dasharatha hurried there to find a boy lying sprawled on the banks of the river with an arrow lodged in his chest. The boy forgave Dasharatha for his unintentional, unrighteous act and demanded that Dasharatha pull the arrow out of his chest. He also told him to take the pitcher of water to his blind parents, who must be waiting for him. The boy died. Dasharatha approached the blind couple and told them about their son's unfortunate death. The parents, grief-stricken, cursed the prince: "Just as we are dying due to the separation from our beloved son, you too shall have the same fate." Dasharatha concluded the chapter by saying that his end was near and the curse had taken effect.