Hi Andyhay
No, that's not a dumb question at all.
It really depends how closely related the parents were. You can get away with breeding brother to sisters but the more you do this, the more problems you will encounter. Close breeding highlights the good but also the bad quite quickly. Any defects or deformities that are present in the genes will appear and hatchability of the eggs will suffer too. Typically, you will get fertile eggs but the chicks will strugle to get out of the shells or die in the shell. The 'ebay' hype of breeding to an unrelated cockerel only means you should have good hatchability and strong chicks, what is hiding genetically in the parent birds will come out over time and the birds you hatch may not look like the parents... this isn't what the show fraternity does, they try to maintain a closed gene pool as much as possible to get the looks they want and then maintain it to get little variation in the offspring.
It really depends on what you want to do with your birds. To create your own blood line like this, you will need to maintain a closed flock and typically would do something called line-breeding (loose in-breeding really) where you might breed daughters back to the father for example. Doing this means you also maintain a closed gene pool so you can slowly eliminate undesirable traits. After a few generations when hatchability is suffering, you can 'outcross' which means bringing in different blood but also new genes....so there could be a load of new problems hidden in the bird you outcross to.
If it were me, I would run a test batch - see how well they hatch and if they are ok, stick with it but don't breed brother and sister again unless absolutely necessary.
Hope this slightly long reply makes sense!
