When parents display a For one child, the others are likely to feel .

favor;  favorite child complex

Explanation:

Favorite child complex is the feeling of complex that arises in the mind of a child out of the favoritism. In any family, favoritism is very common. The preference given to  a particular child or when a child feels neglected in front of the other sibling, the situation gives birth to  favorite child complex. These complexes may or may not be intentional from the parents' end. Such situations arises complexities in the mind of the children and constructs the road of mental heath issues too.

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