There is a mythological reason behind Lord Rama having four brothers. They were the symbol of four Purushartha which are Dharma, Artha, Kama, and Moksha. Lord Rama was the symbol of Dharma, Lakshman was the symbol of Kama, Shatrughan was the symbol of Artha and Bharat was the symbol of Moksha.
Rama or Ramachandra is a major Hindu deity and the seventh incarnation (Avatar) of Lord Vishnu. Rama was born from Kaushalya. Rama was married to Sita, the daughter of King Janaka of Videha. He killed the demon king Ravana, the king of Lanka, and freed his wife Sita, who was kidnapped. He has two sons, Lava, and Kusha.
Bharat was born in Kaikeyi. Bharat is Rama’s younger brother and a symbol of dharma and ideals. Some legends say that while Rama was the incarnation of Vishnu, Bharat was the incarnation of Vishnu’s Sudarshana Chakra. Bharat was married to Mandavi, daughter of Kushadhwaja, and Chandrabhaga, brother of King Janaka of Mithila and thus cousin of Sita.
Lakshman also known as Lakhan or Soumitra, is Lord Rama’s closest companion. When Rama is considered to be the embodiment of Vishnu and Bharat is the Sudarshana Chakra, Lakshman is considered to be the avatar of Shesha or Sheshnaag, the 1000-headed serpent. Lakshmana is married to Urmila, sister of Sita. They have two sons, Angad and Chandraketu. He also served Rama and Sita reverently during his exile.
Shatrughan is the younger brother of Lord Rama and the twin brother of Lakshmana. He is the killer of Lavanasura, the demon king of Mathura, and the grandson of Ravana. He was married to Princess Shrutakirti, the third daughter of King Kusadhvaja.