Homie - urban slang for "a close friend" OR "anyone I grew up with in a certain area" (even if I don't know them) OR "anyone I've shared a lot of experiences with". It is short for another slang expression, "home boy", which means the same; "homie" can refer to a male or female (as opposed to "home boy" or "home girl").
So the line from Akon is roughly saying this:
"You fill many roles in my life. We grew up together. We've had romance, or dated (or had sex). And you are one of my best friends, too."