In Jainism, Sarvartha Raja and Siddharth Raja are both names associated with previous births of Lord Mahavira, the 24th Tirthankara.

According to Jain tradition and texts such as the Kalpa Sūtra and various Jain purāṇas:

• Sarvartha Raja was a previous incarnation of Mahavira. In that life, he was a powerful and just king who practiced charity and righteousness, accumulating great punya (merit).

• Siddharth Raja is the name of Mahavira's father in his final birth, not a previous birth. Siddharth Raja was the king of Kundagrama (near Vaishali), and his wife was Queen Trishala. Siddharth Raja and Trishala were the parents of Vardhamana Mahavira in his last birth, after which he achieved Kevala Jnana (omniscience) and became a Tirthankara.

Relationship:

• Sarvartha Raja and Siddharth Raja are not the same person nor directly related to each other. Sarvartha Raja refers to Lord Mahavira’s own past life as a king, while Siddharth Raja refers to Mahavira’s father in his final human birth.

In summary: Sarvartha Raja = Previous birth of Mahavira Siddharth Raja = Father of Mahavira in his last birth

There is no direct relationship between Sarvartha Raja and Siddharth Raja except through their connection to the soul that became Lord Mahavira.