[Space] Making a solar system with 3 (semi-) habitable planets?

[Anthony]

Originally Posted by vicky_molokh

I'm trying to get 3 planets (not moons) into a solar system

It's pretty much not possible, absent binary stars or some very strong greenhouse effects. The basic problem is that any planet clears a zone around itself, and that forces a separation between planets which is too large for the desired temperature differences.