Most kids are ready for a bike seat once they hit nine to twelve months and...

https://www./parenting/when-can-a-baby-go-in-a-bike-seat-an-age-by-age-guide/

Most kids are ready for a bike seat once they hit nine to twelve months and show strong neck control while sitting up solo. For front seats, you get great interaction. Rear seats provide reliable stability for growing toddlers