May be OK using brothers and sisters. But my brother and I play Rugby, All we have in common is we are both fair players. Buggerd if we play alike. Diferent shapes and skills. Like you our birds show some variation but less each year. Select what you like the birds to do. I think with time they start to show some similarity. Ours are starting to look the same. No introductions this year, and they will all go to 600miles, for two year olds, and 500 for yearlings. I know they may be thin on the ground next winter but ???????????