Yes, it is a rare novelty available only in this world. I am not the only royal here, and setting matters of state aside was already a tradition amongst the others when I arrived.
I think the country would accept it. The harder thing would be accepting it ourselves, since neither of us would want to use someone only for that purpose, and that means finding someone we could both love. And the reverse is true for a foster; I think both of us would readily take a child into our homes and hearts, but many people in the country have ideas about bloodlines. Both of us have brothers, but mine, Kell, doesn't want the throne and I doubt he wants to see his child on it either, if he ever has a child. And both of us agree that Alucard's brother, although he is technically next in line, would make a terrible king. Nor would he make a very good husband, or father, and thankfully, no one has made the mistake of marrying him yet. But I suppose it is still possible that if he had a child, it could be different from him, and might not be a terrible choice.