New customers can not order Family SIMs.
How can I order a Family SIM?
If you already have a BT Mobile plan and want to order Family SIMs, just go to www.bt.com/mymobile, choose your SIM and select that you're an existing BT Mobile customer.
Can I order phones for all my Family SIMs?
You can get an unlocked phone for each SIM via the EE shop.