Twin sibling
A sibling born at the same time — a person whose origin is identical to yours and whose life has diverged from it.
A twin sibling in a dream is the dream's image of a person whose origin is identical to yours and whose life has diverged from it. The twin shares a starting point and is a different person now. The dream brings the twin when something in your life — a road not taken, an alternative self, a peer who started where you did — is currently in view as a comparison. A twin met with affection is the dream affirming the shared origin as a bond. A twin met as a rival, the divergence treated as a competition, is the dream noting that the shared start has been turned into a measure, and both lives are now being evaluated against each other.