Appears to be. Obamas were married in 1992, and he visited Kenya in 1995, BUT if these are from his brother's wedding, that predated his wedding to Michelle, so this would have been prior to 1992. I've seen pictures with Obama and the ring in 1987, and there's a Harvard satirical piece that refers to Obama deflecting questions about the ring on his left hand that was published in 1990.
It's not a wedding ring.