Genetics with breeding

[New duck mommy 2021]

Hello
I’m looking for some help with understanding breeding my ducks
I have a purebred khaki Campbell drake and a purebred Pekin Hen. They had babies that I’m keeping and I have both drakes and hens in that mix.
I have heard siblings are a No but mom to son and dad to daughter is okay but not to do grandpa to granddaughter
I have requests for babies so I want to make sure I do this correctly and not sell birds they could have issues
Any help is appreciated
Thank you
@Miss Lydia
@Pyxis

 

[Miss Lydia]

@Pyxis

I'd be interested in knowing this too, since all I have heard is it takes many generations of inbreeding before there are problems.