[hollowcelery]

Any name can contain a space. For example "Ana Maria" is a common first name which contains a space. On official documents, generally a name will be separated into a given name and surname. In this case "<A> <B C>" and "<A B> C" are considered separate names.

Source: I have a space in my name and some of my different identity documents have the name as "<A> <B C>" or "<A B> C", which causes all sorts of administrative problems.

[CydeWeys]

Leonardo da Vinci is another famous example of a last name with two words in it. It's very common in romance languages. Plus, lots of people in the American south just flat out have two first names or two middle names.

[addingnumbers]

Da Vinci isn't his last name, just like Jesus's last name isn't "of Nazareth" and Cato the Elder's last name isn't "the Elder"

[IncRnd]

Leonardo da Vinci's name was Leonardo, and "da Vinci" refers to Leonardo's birthplace.

[hunter2_]

Documents aside, do you consider <B> to be a given name (parent came up with it) or a surname (parent already had it)? If given, do you consider it optional (i.e., middle rather than first)? Sorry in advance for any shortsighted assumptions about the possibilities here!