Most little riders join the fun around 12 months. Look for strong neck muscles...

https://telegra.ph/Can-Two-Kids-Ride-on-One-Bike-with-Seats-Everything-You-Need-to-Know-05-10

Most little riders join the fun around 12 months. Look for strong neck muscles and the ability to sit up independently while wearing a helmet. Trailers offer great stability for beginners, while front or rear seats keep them close