Combine all fruits with lemon juice in a large pot, and cook over low-medium heat until bubbling and fruit starts to break down. Stir frequently. If desired, add sugar, bit by bit, tasting as you go until it's right. Keep cooking until as thick as you like. You can mash with a potato masher to get out lumps, or else put through a food mill to get really smooth texture. Cool and either put into clean canning jars or else into containers for freezing.