How can only Lionblaze be Squirrelflight's kit?

While he is most likely Leafpool's son, many believe that Lionblaze may be Squirrelflight and Brambleclaw's son due to his pelt color, size, and Tigerstar's interest in training him, as Tigerstar only visits his own kin. Also, some believe that Leafpool couldn't pull off being pregnant with three kits due to her small size. Edit: Maybe Tigerstar didn't know...And his pelt isn't ginger, like Squirrelflight, or dark tabby, like Brambleclaw, it's golden. I know, Tigerpaw says 'our fur colors are alike,' but they're only alike! Leafpool could pull off being pregnant, because in the books, it says 'even slender Leafpool was getting fat.' Coincidence? I think NOT! Anyway, Squirrelflight's milk never came. Suspicious? Very! Tigerstar said he knew that he didnt have his blood so its not possible for Lionblaze to be Bramble ans Squirrels son.