You should find out your compatibility first. Then you can offer your transplant. I would not discuss your medical plans with your sibling and only with the doctor. If you are a match and the recipient chooses blood free surgery perhaps you, if you are the donor, could choose surgery without that restriction. In the USA confidentiality laws limit what can be told to anyone so you could keep your decision confidential.
No need to "out yourself" or discuss it with anyone else either before or after the surgery. Learn to keep quiet and perhaps you can save your sibling.