I used it from birth too, it was fine.

But yeah, if you have the two in there and baby at the top he/she won't be facing you, it won't fit with the seat fully reclined. Actually, maybe it can if the toddler is facing you too but my DD wouldn't want to be down there underneath. So I had them both facing out and with the top one fully reclined DD1 was looking up at me anyway iykwim.