Jealousy is a complex emotion that can arise from various situations or circumstances. In the case of Sophie, she feels jealous of her brother because of her inability to reach unknown areas of his mind. Let's explore this answer in detail:

1. Background:
- To understand Sophie's jealousy, it is important to have some background information about her and her brother.
- Sophie and her brother have a close relationship, and they share a bond as siblings.
- Sophie has observed that her brother often keeps silent and appears to be lost in his own thoughts.
- This behavior of her brother intrigues Sophie, and she becomes curious about the thoughts and emotions that he keeps hidden.

2. Desire to understand:
- Sophie's jealousy stems from her desire to understand her brother's mind and emotions.
- She feels left out and excluded because she cannot access the unknown areas of her brother's mind.
- Sophie longs to have a deeper connection with her brother and believes that understanding his thoughts will bring them closer.

3. Feeling of inadequacy:
- Sophie's jealousy also arises from her sense of inadequacy.
- She compares herself to her brother and feels inferior because she cannot reach the same level of depth and complexity in her own thoughts.
- This feeling of inadequacy fuels her jealousy as she believes that her brother possesses something she lacks.

4. Fear of missing out:
- Sophie's jealousy is driven by a fear of missing out on important aspects of her brother's life.
- She worries that by not being able to access his thoughts and emotions, she may be missing out on key experiences and opportunities for connection.
- This fear intensifies her jealousy and creates a sense of urgency to bridge the gap between them.

5. Need for validation:
- Sophie's jealousy may also stem from a need for validation and attention.
- She may feel that her brother's silent nature and hidden thoughts make him more mysterious and captivating to others.
- Sophie desires to be equally captivating and seeks validation by wanting to understand and be a part of her brother's inner world.

Overall, Sophie's jealousy of her brother is driven by her curiosity, desire for connection, feelings of inadequacy, fear of missing out, and need for validation. She wishes to understand her brother's mind and emotions to strengthen their bond and feel more included in his life.