Could someone explain the inbreeding process within Celestia it's confusing. What kind of 'related' pets can be inbreed and is there a way to delete the inbreed percentage

Inbreeding % doesn't actually affect anything, it was just added as an interest point because some people wanted to know. And no, there's no way to remove it from a pet (since it doesn't affect anything it doesn't really matter in the end.)

Pets cannot breed if they are related within one generation- parents and children, siblings, half-siblings, but beyond that any pets can breed (grandparent with grandchild, aunt/uncle with niece/nephew, cousins etc. all work).

If an ancestor shows up in a pet's lineage more than once within a certain number of generations, that's inbreeding, though I can't remember how many generations back the system checks (5? 9? I literally don't know.)

Ahh thank you that makes sense, i wnated to breed to pets untill i realised that they are half siblings thank you for the help.