This is from Iberia's website (https://www.iberia.com/gb/faqs/iberiaplus/Avios/)

Can another person use my Avios?

You can add beneficiaries to your Iberia Plus card so they can use your Avios for the programme services without you having to accompany them. You can change them whenever you want and update your list of beneficiaries directly by signing into iberia.com > Profile > Frequent companions.

You may be able to transfer from your BAEC to two separate IB accounts and then link them almost like BA Household Account, never tried it though so not sure if it will work but you can always transfer back again