Inheritance
You’re so lucky to know in advance what your offspring will resemble! Here, we have no such guarantees. Sure, generally animals are born to animals, and plants to plants, but beyond that, it’s all conjecture. Your child could be a bacterium or an elephant. It could have two eyes, or a thousand, or sensory organs we haven't yet discovered. There are no hand-me-downs; no general principles in terms of education, care, or nourishment; no assurance you won’t give birth to a multi-tentacled electric ball of rage that kills you as it emerges. Every single time, there’s no way to prepare.