It cannot be folded with both seats on. If I remember correctly, you may be able to leave the rear seat on, but the front seat needs to be removed for sure. It is a pain for sure to remove and replace the seats each time you get in and out of the car. Sorry. Congrats on your twins thwough. =)
If you would like to confirm, please download the user manual from the Perego website.

Good Luck! from Moms Just Know