That is true, the Hesse didn't survive because of that plane crash, and then little Johanna's death, and the heir and his wife didn't have children to suceed to Hesse. If this child had lived, perhaps the succesion would have survived. Also, he might have been good for his sister Elizabeth, although she died tragically young. She was an only child, a rarity among royalty of that time. I agree, the child would most likely not have saved the marriage, although had she not met Kyril, perhaps she would have met somebody else. Ducky was never one to stay in a marriage she defined as a sham, while Ernest woudn't have cared as much.