Hello @sekhar_n
Please follow below steps to minimize confusion:
1. Manually created grouped product
2. Exported it
3. Edited exported file
4. Added your own custom data for prodcuts
5. Imported products
6. Success
OR
Follow below shared steps in given link:
https://firebearstudio.com/blog/the-complete-guide-to-magento-2-grouped-products-and-how-to-import-t...
For more reference: https://github.com/magento/magento2/issues/12793
no longer associate the simple products to the grouped product, Issue fixed in Magento 2.3
Manish Mittal
https://www.manishmittal.com/
