Cain was being snippy with God when he responded, Am I my brother’s keeper? The answer is yes.
We are designed to live in fellowship. We’re supposed to look out for each other. Jesus made it clear with His story of the Good Samaritan. Not only are we to take care of those in our own circle, we should be looking out for anyone in need. Love your neighbor as yourself. That is so important that Jesus listed it right after loving God with your whole heart. Yes you are your brother’s keeper, but that takes effort and time that may not be convenient, money and resources. It’s not easy. But that’s the point. God loves it when we go beyond ourselves for others. He loves our personal devotion, but He loves our commitment to each other just as passionately. They will know we are Christians by our love.