In Jainism, Sarvartha Raja and Siddharth Raja are not commonly referenced as related figures in the main scriptures or traditional stories. However, both names can be found in regional Jain literature or local traditions, sometimes as examples in stories to illustrate moral or philosophical points.

If you are referring to Siddharth Raja (another name for Lord Mahavira before his renunciation—Prince Vardhamana, son of King Siddhartha), there is no direct, scripturally recognized relationship with a Sarvartha Raja.

It is possible that "Sarvartha Raja" could be a metaphorical or symbolic name used in some Jain texts to represent an ideal king or soul who has achieved all (sarva-artha: all purposes), but such a figure is not directly related to Siddharth Raja (Mahavira) in canonical Jain teachings.

If you have a specific context or story in mind, please provide more details, and I can clarify further based on Jain sources.