Hi Carol,

The only cars that will definitely fit three big child seats in (I know those boosters are usually bulky) are those with three individual seats in the back, but there are very few SUVs that have that. The next best thing is a large SUV with a wide back seat. The Koleos certainly fits in that category (assuming you mean the second-generation model launched in 2016), and it has a wide rear seat with loads of space for sure. It appears to have decent room on the seat between the seat belt buckles, too, which I'm sure you know is the pinch point for trying to fit in the booster. 

As all boosters and seats are different shapes and sizes, the only way you'll know for sure is if you bring your child seats with you to try out in the back of a car you're thinking of buying.