WHEN HE WAS SMALL, he was often mistaken for a girl. It was still the fashion in many well-to-do families to dress little boys in gowns of lace and taffeta, and Paula Bonhoeffer considered a skirt a convenience to Fraulein Horn, who must change the diapers. Dietrich''s featherylight blond hair, worn long and curling in corkscrews at the ends to frame his round face, added to the effect. And since three of the four youngest children were girls, strangers who admired Christel, Sabine, and Baby Suse in her pram included the fourth Bonhoeffer "daughter" in their praise as well. "Astonishing," people would say when the children went with Fraulein Horn for a stroll in the Tiergarten, "that two little girls with such different coloring should be twins"--this because Sabine had dark brown hair and black eyes, while Dietrich was fair. Fraulein Horn would nod as she pushed the pram and say, "After all, they aren''t identical twins. This one in fact"--pointing to the blond head--"is a little boy." "You don''t say.

" At three he wore lederhosen and his hair was trimmed to the bottom of his ears, so he was no longer sometimes a she. But with his large eyes and pale skin he was still a beautiful child. Now people said, "With that hair, this one should have been a girl." To make up for it, he tried to act as he thought boys should act. He took charge of Sabine and Baby Suse, not in a bullying way, but in the role of teacher and defender, directing their play and watching out for dangers beneath the bed and beyond the garden wall. He did not know that Sabine felt the same. When the twins sat for their portrait at age seven, it was Sabine''s hand that rested protectively on Dietrich''s shoulder. They lived then in the Bruckenallee, near the zoo.

Sometimes at night the children could hear the animals in their cages, the trumpeting elephants, the grumbling lions, the sharp cries of monkeys and plumed birds. During the Great War, the cries grew more desperate, then weaker. Sometimes they were screams of agony. The oldest brother, Karl-Friedrich, said poor people from Wedding and Prenzlauer Berg would slip inside at night and slaughter the animals, strip the carcasses to the bone, and carry away the exotic meat in bloody sacks. At night, high in their third-floor room, Dietrich spoke with God about the animals, while Sabine remained anchored in the world, watchful. He thought he heard God answer, but still the animals died. Karl Bonhoeffer was Germany''s leading psychiatrist and a great opponent of Sigmund Freud and psychoanalysis. His wife, Paula, was the daughter of Prussian aristocracy.

So it was fitting they should possess a large household. There was Fraulein Horn, the governess. A butler, Schmidt, and two housemaids, Elli and Maria. The cook, Anna. The chauffeur, Keppel. Put during the Great War, even the Bonhoeffers'' bread was more sawdust than flour. The house in the Bruckenallee was near the Bellevue station, and convoys of lorries passed by each day on their way to meet trains bearing the remains of soldiers killed in France. Before long the lorries carried familiar dead, first the relatives of schoolmates, then a Bonhoeffer cousin from Schwabisch-Hall, then von Hase and von Kalckreuth cousins.

Paula Bonhoeffer lost several Prussian nephews. She could not bear the rows of coffins at the Bellevue station, was frantic to keep her children from seeing them, as though they might be cursed by the sight. So her husband moved the family to WangenheimstraBe 14 in the Grunewald quarter. It was a large house with a garden, so the family could grow its own produce, and every evening when lessons were done, the children of parents who had never known menial labor put on their gardening smocks and took up their hoes. Then the two oldest boys, Karl-Friedrich and Walter, were conscripted. Dr. Karl Bonhoeffer could have called upon his extensive connections and obtained safe commissions for them; he was pleased though apprehensive when they rejected such special treatment and requested frontline duties. Dietrich, who was eleven, noted his father''s pride and wished he were old enough to join his brothers.

He secretly followed the progress of the Kaiser''s troops on a map in his desk drawer, blue-flagged pins for the hated Allies, red pins for the Fatherland. The secrecy was necessary because of his mother. In 1914, Christel had come skipping down the Bruckenallee sidewalk calling, "Hurrah, there''s to be a war!" Paula Bonhoeffer had slapped her daughter''s face. When Karl-Friedrich and Walter left for the front, the family and servants walked in a small parade, carrying hampers of food, to the Halensee station to see them off. The parents kissed each of the young men in farewell. More than any thing this marked the solemnity of the occasion, for in the Bonhoeffer family kisses were bestowed only on birthdays and at Christmas. Dietrich thought the day a glorious one until the train pulled out of the station and his distraught mother ran the length of the platform calling out the names of her sons. That night Dietrich paid for his war lust, like a glutton who suffers stomach pains after an evening of indulgence.

He and Sabine shared a room overlooking the garden. The plain oak beds stood side by side with a table between. A cross hung on the far wall--their mother''s doing. It was also Paula who led mealtime and evening prayers, while her husband sat by with a bemused but tolerant expression. Karl Bonhoeffer was an agnostic but believed religions observance to be useful and character-building for women and children. The older boys soon followed his lead and openly expressed their doubts about their mother''s faith, but the twins enjoyed the prayers and the hymns their mother sang as she tucked them into bed at night. They liked to lie on their backs and stare at the cross, iridescent in the moonlight, its surface shimmering as though it were underwater. On the night his brothers went away to war, Dietrich said, "Mama told us good people go to heaven when they die.

But what if they don''t like heaven? Or what if they don''t go anywhere?" Sabine turned away from the cross and shut her eyes. "Don''t think about it." "It''s for eternity," he said. "Think what that means, Sabine. You can say the word over and over and over and over and still not be at the end of anything." He flopped onto his stomach, wrestled the bedclothes a moment, then turned over onto his back again. "Say it," he said. "Say ''eternity.

''" "Eternity," Sabine replied. He began a chant. "Eternity eternity eternity eternity eternity ." "Stop!" Sabine commanded. He fell silent. She heard him breathing loudly. Then he whispered in a terror-stricken voice, "Sabine! I''m afraid I''m going to die!" She sat up. "What?" "I''m afraid I''m going to die, right this minute.

I have to think about every breath. Talk to me, Sabine." "Shall I read to you?" He lay back on his pillow, breathing heavily. "Yes, please." She turned on the light between their beds and found a copy of fairy stories left on the table by Fraulein Horn. She began to read the story of the Wild Swans. By the time the princess sat spinning shirts from nettles, he was asleep. They fell into a ritual then.

Sabine must read to Dietrich, or tell him good night until he fell asleep. As long as he heard her voice, he couldn''t die. Night after night she fought to stay awake so she could keep her brother alive. "Good night." "Good night." "Goodnight." "Goodnight." Goodnight.

Goodnight. Goodnight. Goodnight. Goo-night. Goo-- Most nights, he was still awake when she nodded off. Then Walter was wounded. In his last letter home, he wrote Dear Family, I''ve had my second operation. It was disagreeable, because the fragments of shrapnel were quite deep.

I have been given two camphor injections. Perhaps that will suffice. I refuse to contemplate the pain. Instead, I think of you, my family, with every ounce of strength that remains. Karl Bonhoeffer read the letter aloud to the family gathered in the parlor, Paula seated with her hands in her lap and the children gathered around her. Then he removed his eyeglasses and looked at each of them in turn. "You see," he said, "how Walter writes? He does not seek to deny the pain of his circumstances, yet he is modest. He does not complain.

This is how a Bonhoeffer conducts himself. Your brother is a great credit to our family and to Germany." When word came of Walter''s death soon after, Karl Bonhoeffer called the family together once more to read the official telegram. The children began to sob, and Paula, who was receiving the news at the same time as the others, gave a small cry and stood with a stricken look on her face. Her husband raised his hand and said, "For the sake of the children, my dear, we must show strength and forbearance." His wife looked at him and walked out of the house. The next-door neighbors, the von Harnacks found her sitting in their drawing room, rocking back and forth, mute. They put her to bed for several weeks, and when she finally returned to her own house, she still could not speak.

This continued for several months, until one morning she said, as though nothing had happened, "I think I should like a cup of tea." Her husband took off his glasses and laid them on the breakfast table, kissed her on the forehead, and poured the tea. When the children came downstairs with Fraulein Horn, he said, with a severe glance that warned off.