Yes this might be an albino and it does happen in Siamese litters from time to time.
Scroll down through this site to find info about how siamese is an albino type pattern and that the full albino is recessive to every other abinistic pattern including siamese.
http://messybeast.com/whitecat.htm
With 5 alleles involved it sounds like both the parents are carrying this deeply hidden recessive. You might try breeding them to mates not related to their current partner and see if any more are produced. Good news is albino kittens are not deaf but will need indoor homes to protect them from the danger of sunlight.
But wait to see how this kitten grows up and see if its really going to have very pale blue eyes and flame or cream points - some do.
Hope this helps you!
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