What if...

He keeps his heart in a cage. Locked up, safe, secure. He loves not, hates not, trusts not, believes not. He is neither happy nor is he sad, neither joyful nor sorrowful.
But she manages to get into the cage, and after much care and tenderness, frees the heart and lets it fly. Now he loves, he hates. he trusts, he believes. But most of all, he feels pain...
"A heart once held, can no longer live alone"
He falls for her, and she for him. And as all sad tales go, the end up sleeping together. Then he finds out she is his younger sister.
The one person he trusts, loves and lives for...

What happens now?

Lets talk divorce - Do they qualify? There was no 'unfaithfulness' so it would be called a sin for them to divorce right?
Lets talk incest - Can they really be accused of that? They had no idea until afterward that they were of the same blood.
Lets talk kids - Well oh damn, what is another tragic addition to the mix gonna hurt? Ho do you say 'oh mum and dad are siblings, same way you guys are'?

Now his heart, now a flight, suddenly has its wings clipped. It falls, in no gentle way, and is crushed by the overwhelming feeling of pain that it had been skillfully protected from. Worse still, the cage is no more.
"A heart once held can no longer live alone"
He cannot go back to that cage because once it opened and was emptied, it disappeared. Each cage can only be used once see. Another has to be built and that takes time...at least to get one strong enough to counter or match the previous one.
Originally, in the place of the cage, she stood.
But she cannot help. As strong as she is, she is still but only 'human'. She too would be damaged by the news. She too would hurt from it. And she too, sadly, might have her wings clipped off...

So I ask you the same question they asked Mi, what happens now?