There was some discussion a while back on a related topic:
https://www.volvoforums.org.uk/showt...errerid=184177
We’ve easily got three Maxi Cosi group 2/3 high back boosters in the XC90 and had at one point 3 Group 1 maxi Cosi priori seats in our previous Touareg, so should be fine in the xc90, but you’ll have to ditch isofix in favour of belt fit ones.