What is the difference between loving a girl like a sister in Christ (brotherly love) and being in love with a girl? I constantly have this question in my head.
"Do not rebuke an older man, but exhort him as a father, younger men as brothers, older women as mothers, younger as sisters, with all purity" (I Timothy 5:1-2).
From a biblical sense of the word, there really is no difference between the various objects of our love, whether we are talking about loving God, our fellow men, our parents, our children, or even our enemies. See "Love is Different."
When we talk about loving someone as a brother or a sister, what we are trying to say is that there is no other motivation, there is only our care and concern for that person. When we talk about a boyfriend or girlfriend, there are additional motives. There is the physical, sexual attraction that drives us to hope that one day we might marry the one we desire. There is the strong desire for companionship that goes beyond just a normal friendship, but wanting that person with us for life. These then become the foundations for a marriage. We describe this combination of feelings as "romance."
The hardest thing most young people have difficulty with is seeing the difference between love and infatuation. So many people think they are in love, never realizing that what they love about the other person is what they imagine them to be like, not who they actually are. See: "Dating."