Is it possible to merge 2 accounts into one?

My son created 2 accounts with different e-mails and played in both.
His couch didn't recognize it in time and now asks is it possible to merge accounts to keep progress.

No, it's not.

@Gleb_Pisarev said in #1:
> My son created 2 accounts with different e-mails and played in both.
> His couch didn't recognize it in time and now asks is it possible to merge accounts to keep progress.
How did his "couch" realize it?