I hate to say this but my sister is the same way. I love her with all my heart, but it hurts that we're not close and it's not because of money. What causes greed could be anything from hard times, to jealousy, selfishness, fear, low self-esteem, loss of hope, but I think mostly, sin. 😉
I would suggest praying for your brother because he sounds like he's miserable and needs peace in his spirit.