Would you want to add the baby to your household account (if she's yours ) or to your family and friends list? Either way, you ought then to be able to book for the baby. So if the only obstacle is the fact that the baby doesn't appear in either of your current lists, then that might disappear.

But if you're in a household account and the baby is not in one of those lists, then AIUI you can't book for the baby using your Avios; you'd then have to buy a separate cash ticket from KA. In any event, if you're booking using Avios, you can't do that directly with KA because you have to book Avios tickets through the Avios scheme in which you hold the Avios you want to use.

More information about HHAs in this thread: http://www.flyertalk.com/forum/briti...-accounts.html, including this in the opening post:-