Hello Alan,
The number of axles on a caravan does not dictate what car you use to tow it with. What is important is to choose a caravan that matches the tow capacity of the car or vice-versa.
Each make and model of car is given a maximum tow weight rating by its manufacturer, and this MUST NOT be exceeded. A few cars are not rated to tow anything, and some vehicles can tow well in excess of their own weight (Typically large 4x4's). But the majority of cars can to up to 100% or a bit more, but always check your own vehicles specification.
In general twin axle caravans are bigger than single axle models - but there are some exceptions to that generalisation, so it pays to check specifications.
It is sensible for novice caravanner's not exceed 85% ratio, whilst this usually gives a well matched out fit, it is just as important to ensure the car and caravan are properly serviced, correct tyre pressures, and that both are loaded sensibly.