Yes, I also have two working cockers from the same litter but I didn't realize when I got them that it wasn't a good idea
House training was difficult though as couldn't be sure who had done what and whilst I was cleaning up one puddle, the other one would run through it! Crazy hour really was crazy hour with two puppies doing the zoomies round the room.
Although litter sisters, I don't think they love each other, more a case of tolerating each other. We have definitely never had the problem of them depending on each other more than us.
They do have their spats which sound horrid but usually they are over in less than a minute. Its odd that they would never be aggressive with dogs outside the house, just with each other on occasions. Guess its the same as human siblings
I do love having the two of them as they are so different, both in appearance - one blue roan, the other black, and in character although they do share the same enduring traits common to the breed (always greeting us with gifts, always happy etc).
They are coming up to 11 now and I absolutely dread the thought of losing one of them and just having the one as don't know how the other will react as they have always been together. I had thought a couple of years ago to get another dog so the surviving girl wouldn't feel lonely but I decided not to as I wanted them both to enjoy their twilight years without being bothered by a lively puppy.
I wish you all the best and look forward to seeing photos of them. I feel truly blessed with my two and hope you will be too