what will happen if cats from the same litter mate?

I dont know if this forum belongs here but i was curious
What is possible to happen if two cats from the same litter mate? Will the kittens die or be deformed or aomething like that? Or will they be born normally as any kittens born?

With a little luck nothing especial will happen. But the risk for deformities or other problems increases, it does.  So hope for the best, but be prepared for the worst too....

Some of the "deformities" arent so serious. Perhaps the litter rather small (very typical). Or the cat individs somewhat smaller then usual, but otherwise may be healthy.

The risks becomes of course more serious if the inbreeding continues. Or there was inbreeding in earlier generations.

Good luck!

It depends what recessive genetic defects the parent cats are carrying.