In Jain Dharma, there is no single universal rule about Gotra (lineage) for all Jains. Gotras and endogamy/exogamy customs are mainly community-specific and can vary by region and by Digambar vs. Śvetāmbara traditions.

What is generally understood:

• If a Vidhyadhari lineage has a defined gotra in a particular Jain community, many communities practice exogamy (not marrying within the same gotra). This is a customary guideline, not a rigid doctrinal rule.
• Some Jain groups (and some regional sub-castes) may have no formal gotra system or may treat gotras differently. In those cases, there may be more flexibility in whom one can marry within the Jain fold, as long as Jain principles are kept (ahimsa, satya, brahmacharya, etc.).

Differences by tradition:

• Śvetāmbara and Digambar communities can differ in how strictly they apply gotra-based guidelines. Some Śvetāmbara groups use gotra lists and avoid sagotra marriages; some Digambar communities may emphasize lineage in practice but not as a fixed doctrinal ban. The exact practice depends on the local community and its customs.
• In some parts of India (e.g., Karnataka), cross-cousin and even certain near-relations are seen in Jain marriages, showing that gotra-only rules are not universal across all Jain groups.

If you want, I can point to concise explanations about gotra customs in Jain communities from a Jain Knowledge perspective:

• Intercaste or intra-gotra considerations in Jainism
• Gotra concepts and how different Jain communities apply them

You can read more here and here