Twin characters, aged between ten and ninety-nine? (6-7)
I believe the answer is:
double-figures
'ten and ninety-nine?' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'twin characters aged' is the wordplay.
'twin' becomes 'double' (identical twins are each other's doubles).
'characters aged' becomes 'figures' (I can't justify this - if you can you should believe this answer much more).
'double'+'figures'='DOUBLE FIGURES'
'between' is the link.
Can you help me to learn more?
(Another definition for double-figures that I've seen is " (Into the range of) ten or more".)