How do I find my lost niece and nephew siblings?

Question:

How do I find my lost niece and nephew siblings?

I had lost two niece/nephew sibling after my brother had divorced and his former wife take them and remarried and adopted them when they were little.

Best Answer - Chosen by Asker: This is not the usual issue here, but gotta give the best I can.
EVERYTHING depends on if these children are now adults or not. If they are still minors, and former wife did it legally, she has the legal right to prevent contact. Note I said legal, not moral. And I have experience in my family with a parental abduction, so I know it can be hard.
If they are adults now... the easiest way I can suggest is to locate the new married name of mom. That means having some idea of where the marriage record might be. Many young people have myspace pages, etc.
Good luck... I send this with a layer beyond the standard genealogy reply.