Odoo V9.0c

Hi Odoo community,

I have 3 customers (subsidiaries) of the same company who use the same bank account. I would like to link the same bank account to the three 'partners'. The relation between res_partner and res_partner_bank is one2many... so, I can't.

=> I've tried to create 3 different bank accounts with the same properties (different name but same IBAN).

There is a unicity constraint (res_partner_bank_unique_number) on the property 'sanitized_acc_number' of the res_partner_bank model...so, I can't.

What is wrong in my model ? What should be the good way to do ?

Thanks a lot in advance.