You can fit 3 car seats in a Honda CR-V, but it is difficult due to the middle seat belt being a double latch. (I had 1 hbb, 1 extended rear facing seat in the middle (dd2 was aged 5-7 while using this) and a rear facing infant carrier.
It is also possible to get 3 sears across a Volvo XC90. I had 2x hbb plus a rear facing toddler seat for a couple of years. Now have 1 hbb and 1 large toddler seat (could be rear facing, but isn’t) plus an adult sized teenager sitting across the back seats. I haven’t ever used he back seats regularly, it is possible to get seats to fit.
It depends on which seats you use, as well as the type of car.
It is also possible in a Discovery (had 2x hbb and an extended rear facing seat), but I really disliked the seat belt buckles - they are recessed, so it made doing up seat belts really difficult.
Obviously things like a Viano work (fabulous, btw - the bliss of having enough space to do up seat belts, being able to arrange the seats so that no one can overly annoy anyone else etc is not to be underestimated! But very very large to drive around in)
I would recommend asking the people at the In Car Safety centre for advice. They really know their stuff, and worked really hard to get a combination of seats to fit my CRV when changing cars was not an option.