In Jainism, Tirthankars (including Bhagwan Rishabhdev/Rishabhnath) live a normal human grihasthi (family) life before renunciation, which includes marriage and having children.

So in their earlier life-stage as princes/kings:

• They do marry.
• They do have children in the ordinary human way.
• Their bodies are human; they are not some different “non-physical” species while in worldly life.

Examples from Jain tradition:

• Rishabhdev (Adinath) had queens (Sumangala, Sunanda) and many sons and daughters, like Bharat, Bahubali, Brahmi, Sundari, etc.
• Mahavir Swami in Śvetāmbara tradition is married to Yashoda and has a daughter Priyadarshana; in Digambar tradition he is accepted as lifelong brahmachari (celibate), so there he is said to have no children.

Important points:

1. Before becoming Tirthankar

They are like very pure, dharmic human beings, but still worldly householders (grihastha). Having sexual relation with their own lawful spouse for children is considered a part of normal householder life, not a sin, as long as it is with restraint and without violence or exploitation.

1. After they renounce (take diksha)

Once they take diksha and become monks: - They take a vow of perfect brahmacharya (total celibacy). - No sexual activity at all after renunciation. - Their conduct is absolutely pure in mind, speech, and body.

1. Why this is not like ordinary sensual life?

Even in their householder stage: - Their attachment, lust, anger, etc. are very minimal compared to normal people. - Their main purpose is dharma and karmaksaya (shedding karmas); family life is a temporary duty of that birth, not their ultimate goal. - After deep vairagya (detachment), they leave everything (kingdom, spouse, children) and practice the highest form of brahmacharya till keval-jnan and moksha.

So, summary:

• Yes, as householders they have children in the normal human way with their spouse.
• No, after becoming Tirthankar/muni there is absolutely no sex; they are perfectly celibate.