that kitten is NOT a siamese, because his brother (assuming they are littermates) is an orange tabby, and while oriental shorthaired do come pointed and other colors like tabbies, the likleyhood of someone dumping oritental shorthairs in a box is HIGHLY unlikey...
the kitten IS a colorpoint (marked like a siamese) but probably has little if any "pure" siam blood in him.
he simply looks like a siam because of his coloration...
which makes him a "color point domestic shorthair"
sry its a pet peeve of mine, the shelter down the way labels ALL their cats as whatever breed they resemble and charge higher fees for "purebreds" when the cat has no pureblood in them...
for example ALL blue grey cats are russian blue or russian blue mixes, anything pointed (like that kitten) is ALWAYS a siamese, black cats are always bombays, long haired cats are angora or part angora or persian, if it has blue eyes its "part siames" ect... anything pointed with long haire is a ragdoll or himilayan...*sigh*
COLOR is not BREED.
its false advertising...
unless both partents were siamese (and since the other kitten who is veyr litkley his sibling is not siamese marked, its not likely either partent was siam either...) then its just a domestic short haired with pointed markings.
in good news with a little tlc hes going to be an absolutly stunning little guy who should have no problem finding a home if your mother doesnt like him simply because of his color resembling a siam.