How can I tell my parents I am moving out for good?

This is a tough situation. I understand their feelings but as much as they care for you they are being selfish without even realizing it. I'm not sure how old you are but obviously you are old enough to make your own decisions and be on your own. They should be proud that they have raised you to be a responsible caring adult. If you weren't I doubt that you would be this concerned about their feelings. You just need to tell them that you love them but they have done their job in raising you well and that it is time for you to start making a life for yourself outside of the home.Tell them that you are grateful for everything they have done for you but now the time has come for you to be an adult. Let them know that you will always be there for them no matter where you live. They may not like it at first but they will eventually come around. As awkward as it may be I think it best to talk to them now so that they have some time to prepare before you leave. This way by the time you actually move they will have had plenty of time to come to terms with your decision and will most likely be more accepting of your choice to move out. I think if you just wait until the last minute it will make things worse. They will be extremely upset and may even lose respect for you for not having the courage to discuss it with them before hand. It will be hard but they are your parents and they love you so I'm pretty sure they will still want you in their life even if you aren't living in the home. They will probably try to guilt you into staying but you just need to stand your ground. Letting go is a hard thing to do for a parent especially with having lost your siblings but you just need to remind them that you are only moving, not going away forever. I'm pretty sure it will all work out in the end.