Most kids are ready to ride once they hold their heads up and sit unassisted,...

https://www.primary-bookmarks.win/most-pediatricians-suggest-waiting-until-your-baby-reaches-one-year-old-your

Most kids are ready to ride once they hold their heads up and sit unassisted, usually by 12 months. Choose front seats for babies, rear mounts for growing toddlers, or trailers for maximum stability