what a silly story

Such drama:  A  Spanish official has his knickers in a twist because the Prince and Princess of Asturias were not invited to Prince William's wedding.  Memo to (thankfully) unnamed Spanish official: none of the heirs to the thrones were invited to the Royal Wedding. 

The invitations came from the Sovereign and were sent to her fellow sovereigns. The King and Queen of Norway are invited, but not the Crown Prince and Crown Princess.  This was noted by King Harald's press office it was announced that the King and Queen would attend, and the Crown Prince and Princess would not because they were not sent an invitation.

Prince William did not send out the invitations.  Period. Full Stop,  All the work was done by the Lord Chamberlain's office.

 The Crown Princess of Sweden and her husband, Prince Daniel, are representing the King and Queen.  They did not receive a separate invitation.

King Juan Carlos I is not attending the wedding, and he has designated his wife and son to represent him.  A separate invitation was not sent to the Prince and Princess of Asturias.  If the King had decided to go, and be accompanied by Queen Sofia, the Prince and Princess of Asturias would be remaining in Madrid to watch the wedding on television.
We have seen larger royal contingents at the weddings of the Danish, Norwegian, Swedish and Spanish heirs to the throne.  William is not the heir to the throne.  He is the eldest son of the heir to the throne, and his wedding won't be a state occasion.   This should not be a fuss.

http://www.telegraph.co.uk/news/uknews/royal-wedding/8439151/Royal-wedding-Inquisition-over-Prince-Williams-snub-to-Crown-Prince-Felipe-of-Spain.html