A confusing situation almost arose in a recent game. A LH BG declared a charge forwards into the LH in front of it. The Lancer BG behind said LH failed their test not to charge at the same LH BG. If the target had not evaded both chargers would have had the same route to the target, meaning both would contact in the same place. The Lancers were at the edge of their charge reach. What would have happened if the target stood as the lancers did not have the room to go around?
Lancers
Gap about 2MU then LH
Small gap then Target LH
Let's say the target was Cavalry in one rank that could evade and was disrupted or poor quality so a credible target for LH. Then the Lancers would charge if they failed their test. If the Cavalry evades, both charging BGs charge move, presumably you would move the LH first and the Lancers behind. If they did not evade, burst through would apply and the Lancers wind up in contact with the Cavalry - your one decision would be whether to:
(1) Move the LH charge first, having them burst through, disrupted, and pushed behind the Lancers.
OR
(2) Move the Lancers through first first, in which case the LH are burst through, disrupted, but don't move unless the Lancers need more room to make contact.
For (2) I believe that since a charge was declared, but there is no legal charge move since the target is now being blocked by Lancers, the LH don't make a charge move and that this means they have not "charged" and thus can move normally later.
ADDED THOUGHT ON INTERCEPTIONS:
However, the LH charge declaration might still have affected the enemy - any Interception that occurred or was prevented based on the LH's charge declaration already happened (or didn't) before any Charge movement takes place.
For example, the LH charge path would hit the potential interceptor, or the LH path to contact passes through their zone of interception and triggers Interception, but the interceptors who charge forward don't actually fight because the Lancers's path to contact goes past the ZOI without touching it (which is likely to put the interceptors on the flank of the Lancers, able to flank or rear charge them in their own turn).
NOTE: I don't say the LH's charge is "cancelled" since I noticed that term being used only for enemy interceptions against a charger's flank or rear cancelling a charge, which therefore allows the formerly charged BG to act as if it had not bee charged and intercept on its own. Here, all interceptions have already occurred.