i want to buy 2 isofix child seats(twin gilrs) for my M5/X5 and i was wondering if isofix has an weight/age limit. I checked on a BMW accessory brochure and the isofix Junior seat II says that isofix is limited to 18kgs. Does this apply to all isofix seats in general, or only the BMW versions? cuz if it does apply to all isofix, then i'll just buy the regular child seats.

thanks!