Lilia introduces himself in his dream just as Lilia, with “Vanrouge” as a courtesy name, and we know that Malleus’ grandmother, Maleficia, adopted the orphaned Lilia.
Was “Lilia” the name he was born with, with Vanrouge coming later?
Did he not have a last name at all growing up, just like Silver?
How old was Lilia when he was adopted?
Did “Lilia” come from his birth parents or from Maleficia?
Twst uses the word “courtesy name” (字 (あざな)) to explain “Vanrouge,” and they are an old tradition imported to Japan from China where they were adopted by people upon reaching adulthood.
It can be difficult to tell how the culture of the Land of Briar was using courtesy names back in Lilia’s time:
Is “Vanrouge” a name he gave himself upon becoming an adult?
Was it given to him by someone else?
Is it based on someone or something specific?
And it could very well be linking directly back to Silver’s lack of a last name.
If Lilia adopted “Vanrouge” in the traditional manner (after becoming an adult), it is possible that he has been raising Silver in the same way he was raised, with only one name until adulthood.
Did Lilia intend to have Silver choose a name for himself upon reaching the age of majority? Which would tie back to Silver going out of his way to point out that he will be “coming of age” soon at the beginning of Book 7?
Was Silver finally going to be bestowed with a last name, but then he became trapped at the age of 17?
Twisted Wonderland Reference Note 