In short: The first year of life is the most eventful in terms of the pace of development. The child goes from complete dependence to the first steps and words. Developmental norms are variable: it is important to look at the big picture, and not at a specific date.
The norm range according to the WHO: independent sitting is from 4 to 9 months. If the child is not sitting at 9 months, it is worth consulting a pediatrician.
The WHO normal range for walking is 9 to 15 months. A child who started at 15 months is normal, just like someone who started at 10.
This material is for informational purposes only and does not constitute medical advice and is not a substitute for medical advice. If you are concerned about your child's development, consult your pediatrician or pediatric neurologist.