They made their appearances in 1961 and 1989 -- bookends of the Berlin Wall. Twenty-eight years apart, mother and son both grew up in Berlin, but they might as well have lived on different planets. Barely a month after Katrin was born on July 2, 1961, the Communist-run eastern half of Berlin began erecting a barrier, block by concrete block, until, like a scar, it zigzagged through the city, separating west from east, capitalism from communism, freedom from totalitarianism, family from family. The Berlin Wall would last forever -- or so it seemed to a young girl growing up in its shadow. At the dawn of 1989, she was heavily pregnant with her first and only child, Valentin, who entered the world on Jan. 13. Before the year was out, that world would be entirely different. The fearsome Soviet Union was collapsing. On Nov. 9, 1989, travel restrictions were abruptly lifted, and thousands of East Berliners poured through to the West for the first time. The Berlin Wall had fallen. For Valentin, life has been lived in a city unified in name, if not 100 percent in attitude and mentality. These days, crossing from his apartment in eastern Berlin to his job in the west is a simple matter of buying a tram ticket. To meet Katrin and Valentin is to see a remarkable physical resemblance between mother and son -- the gentle cheekbones, the smiling eyes. But to hear them talk about their experiences of growing up in Berlin is to hear two entirely different stories. 