                     self.texture = textureArray?[3]
                 case .finishHim:
                     self.isHidden = true
+                    siblings?.remove(at: arrayPosition!)
                     self.removeFromParent()
             }
         }

            var moveEnemy = SKAction()
        
            enemy.textureArray = textureMatrix[enemyNumber]
        
            // Add enemy to scene
            switch arc4random_uniform(4) {

    // MARK: Internal enemy state
    var deteriorationStage: Deterioration = .perfectShape
    let deteriorationRate: CGFloat = 0.95
    var health: CGFloat = 4.0
    var textureArray: [SKTexture?]?
    
    // MARK: Sibling information
    var siblings: [SKEnemyNode?]?
    var arrayPosition: Int?
    
    // MARK: Make enemy deteriorate.
    func deteriorate() {
        // If health will pass 3.0, 2.0, or 1.0
        if (Int(health) > Int(health*deteriorationRate)) {
            switch (deteriorationStage) {
                case .perfectShape:
