Two characters making the case for Romeo having married by chance (6)

I believe the answer is:
random
'by chance' is the definition.
(I've seen this before)
'two characters' is the wordplay.
'two characters' means two replacements for 'character'.
'character' becomes 'rando' (I can't explain this - if you can you should believe this answer much more).
'character' becomes 'm'.
'rando'+'m'='RANDOM'
'making the case for romeo having married' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for random that I've seen before include "Lacking regularity" , "Happening without method" , "Roderick came before it" , "Wild" , "Hit-or-miss" .)
