Endosymbiotic theory has it that both chloroplasts and mitochondria were once free living organisms which got taken into bigger cells - they provide the cell with energy, while the cell provides them with proteins and other things.
The two things this question ask about support that theory: chloroplasts and mitochondria are surrounded by a double membrane, which makes sense in that they kept their original membrane and the little bit of the cell's membrane when it engulfed them. And they have some of their own genetic material, though most of it is non-coding, which they have kept from the time when they were independent organisms. Hope that's helpful.
