Just got minor factions, how does it work?

[Muton]

So right next to my home planet is a minor faction. What do I do with it? I waited a bit and it turns out my enemy, another computer AI, has taken ownership of it somehow...what do I do?

[GoaFan77]

You can claim minor factions by sending an envoy cruiser to the unclaimed minor faction world.

If an enemy has claimed a MF world, you must destroy the envoy cruiser. Then it will revert back to neutral, and you can claim it with your own.

[Muton]

Is it worth claiming it or is it worth just conquering it and taking it for yourself? Can an claimed minor faction be part of my trade network with trade ports? Can I build logistic buildings?

[GoaFan77]

They are worth claiming for two reason.

1. Each minor faction has a set of special abilities you can purchase, some of which are quite unique and you cannot get any other way.
2. You get 40% of all income the MF produces, plus it expands your trade network. That may not sound like a lot, but considering you get all this for the cost of one envoy cruiser, and without any build times, it can be a nice early boost to your economy.

You cannot build additional ships/structures at the MF world. The ships their will defend the planet for you, and you get the benefit of any buildings that are already present (research labs, trade ports etc), but you can't build more buildings there. The MF will eventually replace any loses it sustains though.

[z|A|bik2]

GoaFan gave you a deep guide to MF :)
I would just like to add, that conquering MF worlds early on is really costly, both in resources and time. While allying with them, adds a portion of rollplay feeling, and will also provide you with neat economy boosts, and with some luck, some rare abilities.

Later on, you can decide to kill them, in order to take the planet, should you be interested in commiting a genocide. But in any other situation, keeping them as allies, should be better.