oh yeah. no they are just mixes in my book.That might be the reason why that Wellie cross roo popped up.
If the pair are FROM a legbar rooster with three Wellie hens and a partridge Penes hen, then your stock is definately NOT purebred. I would not call them Welsummers at all if that is the case.
If you still want to keep them, enjoy them for their dark eggers. It is possible they may lay a very dark brown eggs, may or may not have terra cotta tint to them.