I need to know is it the doe or buck that define the size and quantity of rabbit kits.
It is a combination of the genes from both the male and female rabbits, so the female will give birth to babies that are a combination of both parents; some will grow up to be large and others will grow up to be smaller.
It is the number of eggs the female produces that determine how many babies she will get each time she gets pregnant.
If the male is a lot bigger than the female, she might get problems giving birth to the larger babies - but this is normally not a problem in rabbits, unless the male is very big and the female is very small.
If the female is larger or similar size to the male, this will not be a problem.