You would have to ask a Singapore lawyer as regards there. As regards the US, she is a minor and you are risking serious legal consequences. Stop...

Is there a question here? It doesn't make any sense to me

This is an immigration question. Please pass to that area.

This is an immigration question. Pass to that area.

I'm not sure there is a question here.

It would help to know what country he/she represents and what the diplomatic immunity would protect.

This is an immigration question. Pass to that area.

If you are in Mexico and the problem is there, hire a Mexican attorney and have him fie suit.

If the children and the parents are in Egypt the jurisdiction is pretty much there. I don't see how hiring a US lawyer would help.

Sure. Hire a Portuguese lawyer and sue him.