css and/or SASS + (sibling) selector upwards [duplicate]

SASS supports all CSS3 selectors. Sibling + selector is one of them. But it does not bring some extra features.
It means you can do

.first {
    + .second { 
        font-size: smaller;
    }
}

But you can’t impact a parent with it…

P.S. It seems to be a feature of CSS4.