BA has program were you can setup "Household" account:
From BA website:
As an Executive Club member you can invite up to 6 people to join a Household Account.
Our Household Account enables you to pool your BA Miles with up to 6 other members of your household, so that you can enjoy the membership benefits of the Executive Club collectively.
Please note you can only pool together your BA Miles and NOT your Tier Points, as members of a Household Account.
All members applying to set up or become part of a Household Account must permanently reside at the same residential address.
Business addresses are not permitted for Household Accounts.
Family members of any age can join the Executive Club as part of a Household Account.
Any member of the Household Account who is aged 18 years or over, can redeem the BA Miles collected.
Please note: Any BA Miles collected by a member of a Household Account can only be redeemed by members of the same Household Account and not by other members outside of that specific Account.