I am wondering if it matters what drakes are used. Like does it matter if it's the dad, brother, or son drake that is used for breeding (the daughter, sister or mom). My ducks are for pets, eggs and meat.
Firstly, welcome to the world of ducks! To answer your question, you can technically get related ducks to mate but there are health risks and higher risk of birth defects for the ducklings just like there are for all animals in that situation. You could risk it and things might go smoothly but they also could go awry very easily and as a duck owner I wouldn't want my first hatching experience to go that way. Also it's extremely easy to find drakes as nobody wants them.
Some hopefully helpful tips:
-Never feed them bread or anything meant for human consumption like leftovers
-Corn and scratch grain is a good treat but better in small portions
-They are VERY messy
-They're poop machines!
-There's a fantastic list on this website called 'The ULTIMATE List of Duck Treats and Supplements' It's extremely helpful
-They get very attached to one another
-Since you'll have drakes and hens they need to be on food compatible for them both so NOT laying feed this means you'll need to give the hens oyster or egg shells in a container apart from the regular feed so her eggs will have strong shells
-Hens can become egg bound which means the egg is stuck inside of them because there is no or little shell
As far as mating related birds, birds are far less susceptible to issues related to inbreeding and linebreeding when compared to mammals. Many, many chicken and duck breeders rely on inbreeding and linebreeding to develop the characteristics desired. It takes many generations for problems to occur. That being said, there is a greater chance for unwanted characteristics to occur if both parents carry the genes for it. That's why good breeders cull many birds; they don't want those birds passing on their genes. Of course if you are just looking to raise some backyard ducks and aren't looking to become a breeder you don't really need to worry about such things.