Breeding Techinques

Question
I'm wondering your views on this subject,
should I breed a grandchild(cat) with her grandad(cat)??? or maybe grandad with great grandchild
These cats are a wonderful chocolate colour, not like other cats that is why I was wondering.Please keep in mind these are healty cats, treated with the best of care.
Any would be greatful
Thank you.

Answer
This is listed as a pending question, but I thought I had answered it already.
I have two views on this subject
One concerns the passing of defects from parent to offspring when the mating is too close. The defects could be hidden and this close mating would reveal them in the kittens. Then ist is too late.
The second concerns attempts at establishing  a particular trait or colour. If that trait or colour does not currently exist then a close mating will help establish this but then future matings should be carried out very carefully and only if the line breeding is necessary