The blackberry and sidekick plans are separate from your T-mobile service plan. The data plan simply gives u access to the extra features of the phone, like e-mail, internet, IM, etc. So if you wanted to get one blackberry and one sidekick, you would have to add those plans to the respective lines on your family plan. Every line does not have to have a smartphone/PDA plan just because one or two of them does. It is usually about $19.99-$29.99 extra per month depending on if T-mbile has a special.