In between name (Denmark)

Until rather recently one personally had a

a) first name (of which "count of" was a part)

b) a family name.

Now one have a

a) a first name (Danish: "Fornavn[e]", name before, without "count
of")

b) an in between name (Danish: Mellemnavn[e])

c) a name behind or after (Danish: Efternavn[e]).

The name of the actual head of State is therefore: Margaret - Queen of
- Denmark.

The term family name has also changed (initially : family name, then
lineage name, now as said: name behind or after)

Charles von Hamm...

By this do you mean a forename, a middle name and a surname? The forename
and the middle name(s) are collectively the given names.

Dag T. Hoelseth...

No, at least in the Scandinavian countries a middle name is (legally
defined as) a surname inherited from either the mother's or the
father's side and is, as the expression indicates, in the middle
between a forname (given name) and a surname.

In the case of Margrethe II, her forename is Margrethe and her other given
names are Alexandrine Thorhildur Ingrid. If the Efternavn(e) is equal to a
surname, then the Queen does not have one (although Her Majesty always has
the option of making "of Denmark" the surname for members of the Royal
Family).

Dag T. Hoelseth...

Queen Margrethe II has as you suggest four forenames (given names) but
no middle name and no surname is used (although this is required by
law). I gather that she is registered (in the Public Register) with her
title as "surname", like her ancestors were in the various censuses.

Dag T. Hoelseth

Charles von Hamm

edespalais...

Unknown is, if anybody who does not belong to the nobility can have an
"in between name"