Based on the description, <span>marvin is exhibiting :Decentering
Decentering is a psychological distress that happen to someone after being replaced from the center of attention.
Before Marvin's brother is born, Marvin received the full attention from his parents. But now after his brother is born, most of the attention is given to his brother, which is the most likely reason why Marvin is upset
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The greek alphabet formed the basis for latin, which is used in many European languages today. So Greek.
