I'm going to have a baby soon. I was baptised and rose Catholic. My husband is Greek Orthodox. We want his brother who os also Greek Orthodox and my sister who is Catholic to be Godparents. In what Church can we do that?

In the RC church I believe that they would allow only your sister to be a Godparent. As a christian your brother-in-law could be designated to be a "witness," but since he is not a RC he can not be a Godparent. Recall that the role of the Godparent is to assist in raising the child up in the faith. For Roman Catholics that includes allegiance to Rome and the belief that the RC church is the one true church. So clearly the Godparent must be Roman Catholic.

As you might expect most protestant churches don't draw such rigid lines. My own child has a RC Godparent even though we are not RC. I'm not sure what the Greek Orthodox church would have to say about it.

In both cases I believe both churches would restrict, the Orthodox are often more strict than the catholic.

But your start would be talking to the priest at your local parish and see if they would allow it. While perhaps not always proper, I know many local priests that don't always follow all rules exactly.

Next of course the Anglican church would allow this.