Wait for age 9-12 months when your child sits independently and holds their...

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

Wait for age 9-12 months when your child sits independently and holds their head steady in a helmet. Trailers offer maximum security, while front or rear seats allow for more connection. Start slow and keep rides short for happy, safe family trails.