Add to a mixing bowl, add sugar and 2 cups of water then mix.
Dice citrus peel and add to a pot together with 3 cups of water. Boil for 10 minutes.
Place a sieve over the pot and strain the citrus juice mix into the pot.
Bring to a boil then simmer for 40 minutes.
While the fruit is cooking prepare the jars as indicated here. Set aside when done.
Remove the pot with the cooking citrus from stove and add to a blender. Mix until smooth. Note: you may need to do this step in batches, depending on how large your blender is.
Return the puree to the pot, and simmer over low heat for 15-20 more minutes or until the marmalade is thick enough, as preferred, and darkens in color. You may need to adjust the heat in order to prevent boil over and you'll need to stir frequently. Be careful if not using a large pot, as the mixture will bubble a lot and will make a big mess on and around your stove. Also make sure you protect your hands and arms.
Pre heat oven at 360 F
Transfer marmalade to the prepared jars. Place a kitchen towel to the bottom of a large pot and add the jars. Add water as much as the pot can hold then place it in the oven and leave to boil for 10 minutes. Do not boil the lids as this will damage their adhesive rings so make sure the water in thee pot is below the lids. Leave to cool completely in the oven.
Unopened marmalade will last up to 6 months. Once opened, store in the fridge.