No character Slot from HOT Expansion.
The free slot is given out in batches every Friday. It doesn’t matter where you bought it, the only requirement is the age of the account and adding a HoT serial key to it prior to launch.
If you’ve waited over a week, contact support.
Too be honest there could be lots of reasons why, for example:
Did he also purchase the expansion through Amazon or Did he purchase directly from Arenanet?
Did you both get the same version? If you got standard and he got the deluxe/ultimate version, those actually have two slots, one which is part of the pre-purchase and a second for being a veteran.
The veteran slots are delayed by a few days, they did not apply immediately.