The only way to move points between accounts is by paying a ridiculous transfer fee.
When you transfer your Asia Miles to your redemption group members, a service fee will apply. The minimum block transfer is 10,000 Asia Miles at a service fee of USD170, and further blocks of 5,000 Asia Miles can be transferred at USD140 per block.
So you need to do this either by transferring enough points from Amex into one account to book 2 tickets or make two transfers, splitting the points so that each CX account has enough points for one booking.