It is possible, you can cross Silkies with anything and get back to the Silkied feathers in two generations. What is harder to keep is the correct body shape, blue ears, black skin and the 5 toes. Those hard feathers and the red combs to me says they were a cross in the not too far past. They look like Silkies again, so I guess you have some really hefty pet quality Silkies. I think the Silkies out of a Showgirl pen are larger and heftier than the Silkies. I also agree they are MUCH older than 4 months - your two boys appear to be at least 6 months old. Well that only means you are closer to eggs from the girls