I also has problem identify my first 2 litters of BSH and SF as all 3 of my male BSH are blue and all my SF/SHH are blue silver spotted tabby. With subsequent litters I weigh my kittens every day. I can tell them apart by their weight, size/length, colour tone, pattern and features.

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Manekineko Cattery http://www.geocities.com/hueyleehl/index.html
Breeding pedigree Scottish Fold and British Shorthair