In short, the basic concept I have is two habitable moons orbiting a gas giant which itself is orbiting either a main sequence star or binary system of some kind.
As long-standing SE explorer (although I don't have many records) I could say that even though gas giants in habitable zone is very common occurrence, the life-bearing planets around them are very, very rare. Since I've checked last version, it became much easier to find desirable parameters for planets, so I've found a lot of worlds similar to Earth, so I'm pretty sure it is possible that such system indeed exist somewhere among billions of stars in our galaxy. But it would be very difficult to find a habitable world near gas giant, save for two in the same place. Maybe ocean worlds are acceptable too?
There is a tool now to find nearby stars, and moreover, it can also search for planets with certain parameters, but as it is very rare, you may spend hours and hours searching and find nothing. I might actually spend some time looking specifically for this type of planet so I can gather some statistic to understand what is considered to be "realistic" in this version.
Otherwise, it is possible to look into "Modding" part of the forum - there are several instructions how to create a planet manually, but I never actually bothered to do it myself. You have to study a bit and do a lot of practice, but this is most reliable way to acquire desirable parameters.