In Jain dharma, the key is dharma (righteous conduct) and ahimsa (non-harm). Here’s the simple guidance:

• For laypeople (householders): Sex is allowed only within a lawful, committed marriage. Fidelity and mutual consent are important. There is no requirement to convert or to be Jain by birth or faith to have a marriage or intimate relationship.
• For monks and nuns: Celibacy is essential; sexual activity is not allowed.
• Interfaith marriages: Jainism does not prohibit marrying someone from another faith, but individuals may face additional personal or family considerations. What matters is living truthfully, non-harm, and mutual respect within the relationship.

If you’re seeking a more detailed Jain perspective on marriage, fidelity, and interfaith considerations, tell me and I can explain further in simple terms.