Just to add that… when you spend Avios they are deducted proportionately from each account. A couple of examples:a) if you booked yourself a reward flight for, say, 12,000 Avios it would take 6,000 from each account leaving 5,000 left in each one.

b) if you continue to earn Avios and in a few months you had 22,000 in yours (and still only 11,000 in your son’s account), then that same 12,000 Avios reward flight would take 8,000 Avios from your account and 4,000 from your son’s account. So leaving 14,000 in yours but only your 7,000 in your son’s account.