Cardverse!Hetalia x Reader : The Missing Ace

The Ace had been missing for a few years after the great war between the four kingdoms; Spades, Hearts, Clubs and Diamonds.
These kingdoms tend to make an alliance with the Ace, whom was the strongest kingdom and make a wonderful yet powerful allied.
In the other world, Reader-chan and her little brother are the last Ace. The spies from the other kingdoms had noticed that Reader-chan and her little brother had the quality of an Ace.
At the Kingdom of Spades, the Queen of Spades, Arthur had devised a plan to get Reader-chan and her little brother to their side since the Ace was famous for its battle and friendship with the Spades but the other kingdoms want Reader-chan and her little brother.
Now, the question: Which kingdoms will Reader-chan and her little brother will choose? How will Arthur's plan going to work? Will Reader-chan and her little brother find out her family past, especially their history?
Read this to answer all this questions. Good luck to all.