I found a mistake on an official LEGO page and I am going to write to them.
Despite what I’ve read and heard before (including Wikipedia) I received this explanation, which I consider a reputable source:
“Thank you for your e-mail.
Actually Ole Kirk Kristiansen’s surname is spelt with a K. The name on the birth certificate is spelled correctly. I is a misunderstanding, that the name should be misspelled on the birth certificate.
In Ole Kirk Kristiansen’s day, however, it was common practice for the surname Kristiansen to be spelled with either Ch or K – and Ole Kirk Kristiansen did indeed use both versions, although mostly the Ch style. When signing legal documents, he used the Kristiansen. In our archives we have several documents with both signatures: Ole Kirk Christiansen and Ole Kirk Kristiansen.
Both Godtfred Kirk Christiansen and Kjeld Kirk Kristiansen – like Ole Kirk Kristiansen before them – were baptised Kristiansen, and Kjeld Kirk Kristiansen has always used this spelling. Godtfred Kirk Christiansen, on the other hand, used the Ch version all his life, except when signing legal documents, and was in fact popularly referred to as GKC. With the amendment of the Danish Act on Names in the 1980s, it became possible to change one’s surname – and Godtfred Kirk Christiansen did exactly that, formally adopting the name Christiansen.
The reason the names Ole Kirk Kristiansen and Kjeld Kirk Kristiansen are written with a K is simply that it is how it is spelled in their birth certificates. Godtfred Kirk Christiansen, on the other hand, is spelled with Ch because he himself always used that form – and because he officially changed his name to Christiansen in the 1980s.
Kind regards
Tine Froberg Mortensen
Records Manager
LEGO Group Archives, LEGO Idea House”