W sitting is often seen in early years, especially when trunk and hip control is not fully developed. It is not the desirable position as sitting so for long hours causes postural and orthopedic problems.
Next Steps
Strengthening core muscles by repeated sitting and standing, making them reach for toys infront and at back while sitting can help.
Repeated verbal cues to put the feet at the front, or repositioning them yourself will settle it slowly over time. Patience is the key.