A flex container is always the parent and a flex item is always the child because the scope of a flex formatting context is limited to a parent/child relationship.
Descendants of a flex container beyond the children are not part of the flex layout and will not accept flex properties.
You need to always use −
Some flex properties apply only to flex containers −
justify-content flex-wrap flex-direction
Some flex properties that apply only to flex items −
align-self flex-grow flex