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She doted on him much more than the other two kittens.
Literal
She [topic-は] other [genitive-の] 2-counter [genitive-の] kittens [more-than-より] much him [object-を] doted-on.
Two patterns. ずっと ('much, far, by a wide margin') is an emphasizer for comparisons — Aより**ずっと**好き ('much more than A'). 2匹 uses 匹, the counter for small animals (cats, dogs, fish, insects). かわいがる ('to dote on, treat tenderly, cherish') is the standard verb for showing affection toward pets, children, or anyone smaller — covers both 'love' and 'fuss over.' The contrast in the sentence (he vs. the other kittens) suggests favoritism among siblings, a familiar dynamic.