You could always take the masculine form of your birth name, or what your parents would have named you if you'd been born with the right parts, and post on a baby name board asking what names would sound good with that, as siblings, as one way to generate ideas. Especially if you actually *have* that sibling - they're not going anywhere.
You may want to rule out anything so trendy that nobody was naming their children that back when you were born, and those that remind you of people you didn't like from your childhood before anything else when you hear the names. If you always think of "Bratty Bradley" from kindergarten when someone introduces you to a Brad, it's probably a bad idea to give it to yourself.