...people have always sought a right reason for people to feel self-motivated to love each other...
That's the problem right there if you ask me. That seems based on the premise that people aren't capable or naturally interested in being kind to each other, which is not necessarily accurate.
In any event, science can explain many things way better than religion, but I'm not sure that something like love can be scientifically explained, or how can it promote loving each other, other than by choice. Although many religions preach "love", but not to gay people, not to fornicators, not to rape victims, and for as long as they say it's the right thing to do, otherwise people deserve to die.
There's no science or religion that can make that right in any way shape or form.