A note on forehead kisses
I find that the highest form of showing true, pure love for someone else is to kiss them hello or goodbye on the forehead, or even on the head (to kiss their hair). It involves the other person being usually engaged in something else, and there seems to be an implicit notion of not having to reciprocate the greeting because of the nature of the relationship in which this takes place. A simple  smile, or quick raise of the head from the receiver means acknowledgement.
It’s a symbol of protection, understanding, warmth, home. One overlooks the state of the other person’s hair or head. It doesn’t really even matter if their hair is greasy or a bit sweaty. It is the utmost expression of fondness for someone else.