When my friend got married, his brother met the sister of the bride at the wedding. They also fell in love with each other and wanted to get married - but the parents stood up the wall - how, you are now relatives!!! They were the parents of both sides. It was not so long ago, 15 years ago.
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Even the PC allows it. Or is it a small nation with stupid rules from the depths of centuries? You could go and register quietly.