If its SSRS 2008, make available the "Grouping window" by right clicking on report and selecting "Grouping" from menu.
1. Select "Advanced Mode" ( click on small arrow on right corner of grouping toolbar) this will display all rows of tablix control.
2. Click on the desired static row and press F4 to display properties window.
3. Set "RepeatOnNewPage" to "True" and
4. Set "KeepWithGroup" to "After"
5. Set the property same for all static row in same hierarchy i.e if you have 3 rows before group header in tablix then you need to set these properties for all. otherwise SSRS will display an error.