If you take out more than one eligible Family Plan mobile contract on the same account you’ll automatically get a discount but this will not show on your initial contract as the discount, this will be added to your account when you start your contract with us.
You can find more information about the family plan on this link here.
Virgin Mobile: "Just sign it. Don't worry about what the contract says. Don't worry about what you're agreeing to. We'll tell you what you've agreed to AFTER you've signed it. Trust us, it's fine".
It's a legally binding contract! You won't have a leg to stand on if when they mess you about, and good luck getting hold of anyone and explaining what's happened if it all goes south after you've signed that!