I have created an library (A) that uses several other GPL v2 or v3 licensed libraries (B,C,D) which, I am not the author of. I am only the author of A.
Can I license library A under a GPL or a dual license and use it in a commercial software which will be licensed only under proprietary license ?
Similar question have been posted here and there but don't address the fact that other GPL licensed libraries might be re-used in the main library (A).
A software which includes (links to) a GPL-licensed library, whether directly or indirectly (thus as a library called by another library), needs to be released under GPL. You link GPL-licensed software, and as such your library is a derivative of those and needs to follow the license terms; the license gives you no right to distribute it under different terms.
Things look different, if we talk about the LGPL, thus GPL with linking exception.
You may, of course, sell additional guarantees or indemnification to clients for your library or programme - but even that doesn't lift the obligations put on you and your library's clients by the GPL introduced by the dependencies of your library.
