Allow Alone Time
Even though you are probably much closer to your sibling than you would be to another roommate, you still need to allow your sibling some alone time. You may share some common areas in the apartment, but that does not mean you need to be together all of the time. Go into your room sometimes to give your sibling some quiet time. You should expect the same back in return.
Divide and Conquer
For a lot of siblings, working out the food situation and the housework is often the most difficult part of living together. That is why it can be helpful to have separate areas of the house that each of you is responsible for. One of you can clean the kitchen for a week, while the other one does the bathroom and living area. The next week you can switch. As far as food goes, it is a good idea to divide the fridge and pantry into two sections. That way you can each buy your own food and eat your own food. If you want to share, that’s fine, but you should always ask before helping yourself to your sibling’s stock.
Living with your sibling can be very rewarding. As long as you set some ground rules and stick to them, you will be able to build on your lifelong relationship to make it stronger than ever.