Bug Fix "van Son"
The last name "van Son" should be accepted as a valid last name. FamilySearch needs to handle international naming and not make generic systemwide assumptions that the word "son" shouldn't be in the last name. People are renaming people as "vanSon" to get around the bug, but it would be much better to fix the bug.
Here's the article that explains that "son" is invalid (when it's not):
Here's a couple of example records:
On sealing to spouse it says invalid last name, but it's correct and giving appropriate research hints:
Here's one where someone changed the last name and explained it's due to the bug in the comments: