If you have 4 T-mobile cellular phone lines, is texting free?

I currently have Cingular/Att but my contract with he company ends in July I plan on getting T-mobile cell phone service with four lines, one for each person in my family. Will my contract include free unlimited texting? If I get the family 4 line plan, will I get free unlimited texting with my contract? http://bit.ly/p061Id