how to solve merged mining conflicts among coins with different block time

[langyu]

As we known，  nmc and bitcoin both have  block time of 10 minutes , what about  huntercoin (2 minutes) ? 
Are there any special in huntercoin (auxpow block） data structure，  for example  the prev_hash in parent block  header are all the same ? 

Field Size   Description   Data type   Comments
4   version   uint32_t   
32   prev_block   char[32]   
32   merkle_root   char[32]   
4   timestamp   uint32_t   
4   bits   uint32_t   
4   nonce   uint32_t   
 ?   coinbase_txn   txn   Coinbase transaction that is in the parent block, linking the AuxPOW block to its parent block
32   block_hash   char[32]   Hash of the parent_block header
 ?   coinbase_branch   Merkle branch   The merkle branch linking the coinbase_txn to the parent block's merkle_root
 ?   blockchain_branch   Merkle branch   The merkle branch linking this auxiliary blockchain to the others, when used in a merged mining setup with multiple auxiliary chains
80   parent_block      Block header   Parent block header
 ?   txn_count   var_int   
 ?   txns   tx[]