It's a circle. It began with the beginning of time, and will finish at its end.
In his minds eye, Kakashi sees the Sannin, but they are younger, much younger. He sees Sandaime with Tsunade, Orochimaru, and Jiraiya. They are only 10, and are teetering on the edge of adulthood. They were smiling, except Orochimaru who was smirking.
In his minds eye, Kakashi sees Jiraiya, and his team. He sees the future Yondaime, sees his partners, a young girl, Kisa, and an equally young boy, Hiro. Twelve, they are twelve, the war has been over for several years and there's no need. Their smiles are stretched so far that Kakashi wonders why their faces didn't spilt.
In his minds eye, Kakashi sees his sensei. He sees himself, Rin and Obito. They were born into war. Only 13 and already innocence was fading. They try to smile, but their eyes betray their true feelings.
In his mind's eye, Kakashi sees himself, older now. He sees Sasuke, Sakura and Naruto. They were still children. All but Sasuke, who was not-quite-an-adult-but-not-quite-a-child.
In his mind's eye, Kakashi sees Naruto's team. Again, just like always, two boys and a girl. All young children, their smiles true and happy.
The wheel spins and time passes. The cycle weaves on, always there are small differences, but the pattern remains the same.
I make no profit, this is for personal entertainment purposes only. Cliche I know..