If you find
It is not always clear who is related to who else
AND
Selecting a member of a family (plant or animal) as seedstock means bringing in some family characteristics that are desirable and some that are undesirable
Then,
You need to be able to connect the dots linking family members together. This is not always possible, but the better the linkages are understood, the better your chances of controlling which characteristics future generations will inherit.
Once you select a plant or animal to breed from or to cull, you can use genetic links to relatives to decide whether to keep or cull a whole line of them.
If you want to select animal or plant seedstock, you need to know who gave what.
It is no use selecting seedstock unless you first get seedstock evenly assessed so they are on a level field. Then if one animal or plant seems better than the others, it is likely to be because it is superior. If the field is uneven, one may stand out not because it is better but only because it had some advantage the others didn’t.