I need to ask few more questions before answering your query. Early consultations can prevent complications. Kindly contact me on whatsapp chat  (84960595 six five) Dr Faisal Zoheb MBBS , MD PAEDIATRICS , PGPN (BOSTON), FELLOWSHIP IN NEONATOLOGY ( Newborn and vaccination specialist )

Greetings At 16 months, achieving independent walking is an excellent milestone that indicates strong motor development, though a curved or slouched posture while sitting can sometimes appear prominent due to developing core and spinal muscles. The slight bending of the back during sitting could be a normal variation of early postural habits, or it could potentially indicate mild trunk weakness, structural spinal alignment variations, or early orthopedic conditions. Kindly consult Pediatrician in person