Convertible Car Seats for twins

Around the first birthday, twins outgrow their infant seats and you buy two convertibles. The twin question here is width. Two convertible seats have to fit across your actual back seat, and if a third child is anywhere in your plans, three-across becomes the constraint that picks the seat for you. Measure your bench before you fall for anything.

Narrow-profile seats exist for exactly this reason, and the difference between a 17-inch and a 20-inch seat is the difference between fitting and not. Buy new for both, same rule as infant seats: crash history is invisible, and expiration dates are real. Spend your used-market energy on gear that does not restrain a baby at highway speed.