What is unconditional love? It is the affection given to another person or persons without expectation of love or benefit in return. It is a lovely idea. It is also a crock of shit. There is always a reason. 

Love is an evolutionary adaptation. People who don’t love don’t reproduce, or if they do, their offspring have a vastly reducted probability of survival. Millions of years of evolution have favoured species who copulate, protect the gestating females and protect offspring until they are old enough to look after themselves. Evolving man didn’t figure this out for himself. It was trial and error until a species evolved that registered pleasure when it did what was necessary to perpetual and protect the species. We call that pleasure, love.  

It is an easy step for love of group, protection of other group members and their offspring to become an evolutionary advantage in group selection. 

There is always an element of self interest in love.