Hi Rajendra,
Creating a BRF rule in this case would be complex, you can probably create a custom agent rule by merging following function modules to create your own logic
GRAC_MSMP_ROLEOWNER_AGENT
GRAC_MSMP_AR_ROLE_ALT_APPR
In forst one you would get roleowners, you can then compare them with the user in request and based on your condition you can find out alternate role owners from second FM.
Best Regards,
Aman