Contract does not change, however since the plan is in his name, when you leave, you will lose plans that are no longer offered and have to sign up with current plan calling and data plans. Since he is not leaving the account, just removing your line, his data plan he can keep, he will need to change to a current calling plan since he is no longer on a family plan.
This is a user to user forum. I am a user, just like almost everyone else on the site.
*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.