Is it normal for a half-month-old short-legged cat to split its hind legs?

Not normal. The reasons are very complicated, such as the kitten's natural malnutrition and calcium deficiency, the mother cat's lack of milk and nutrition, the kitten's shrinking injury and the kitten's lumbar injury. The first two cases can be improved by feeding goat milk powder or other canned nutrition (if there is a female cat, it should also be supplemented with nutrition), while the latter two cases have poor prognosis and cats are difficult to survive.