In the anime at least there is a scene where Tsunade is looking over the teams and makes a remark about how they have been grouped together the same way their parents were grouped together. Like how Ino, Shikamaru(sp?), and Choji's fathers were all in a team, and that we see them fighting together during the sand/sound attack and saying how it was just like old times. This makes sense since the families usually have their own fighting styles and signature jutsu's. Like Shikamaru's family specializes in shadow possetion and Ino's family speciallizes in temporary Soul Transfer and Choji's family specializes in body expantion. So it makes sence to team up these families from genration to generation because they're abilities work well together.
Also I noted another common theme in some of the teams we know about in the past. Like how the teams were either taught by a future Hokage, or someone who was taught by a Hokage. In a couple of instances the teams even had somone related to a Hokage. Like how the Senin were taught by the 3rd and Tsunade is the grandaughter of the 1st. Juraiya was taught by the 3rd and latter taught the 4th. Or the the 4th taught Kakashi, who would end up teaching the 4ths son, Naruto. It seems to be switching between being taught by a hokage and then one of their students would end up teaching someone who would becomes hokage and the cycle repeats again.