diff --git a/Sources/FirebladeECS/UnorderedSparseSet.swift b/Sources/FirebladeECS/UnorderedSparseSet.swift
index d7bbca0..8d07370 100644
--- a/Sources/FirebladeECS/UnorderedSparseSet.swift
+++ b/Sources/FirebladeECS/UnorderedSparseSet.swift
@@ -5,7 +5,7 @@
 //  Created by Christian Treffs on 30.10.17.
 //
 
-open class UnorderedSparseSet<Element>: MutableCollection, RandomAccessCollection {
+open class UnorderedSparseSet<Element> {
     public typealias Index = Int
     public typealias Key = Int
 
@@ -28,7 +28,6 @@ open class UnorderedSparseSet<Element>: MutableCollection, RandomAccessCollectio
 
     public var count: Int { return dense.count }
     public var isEmpty: Bool { return dense.isEmpty }
-    public var capacity: Int { return sparse.count }
 
     @inlinable
     public func contains(_ key: Key) -> Bool {
@@ -126,19 +125,10 @@ open class UnorderedSparseSet<Element>: MutableCollection, RandomAccessCollectio
         return (denseIndex, entry.element)
     }
 
-    // MARK: Collection
-    @inlinable
-    public func index(after index: Index) -> Int {
-        return dense.index(after: index)
-    }
-
     @inlinable
     public subscript(position: Index) -> Element {
         get {
-            guard let element: Element = get(at: position) else {
-                fatalError("no element at index \(position)")
-            }
-            return element
+            return get(unsafeAt: position)
         }
 
         set(newValue) {
@@ -146,18 +136,17 @@ open class UnorderedSparseSet<Element>: MutableCollection, RandomAccessCollectio
         }
     }
 
-    @inlinable public var startIndex: Index {
-        return dense.startIndex
+    @inlinable public var first: Element? {
+        return dense.first?.element
     }
 
-    @inlinable public var endIndex: Index {
-        return dense.endIndex
+    @inlinable public var last: Element? {
+        return dense.last?.element
     }
 }
 
-extension UnorderedSparseSet.Entry: Equatable where UnorderedSparseSet.Element: Equatable { }
-
-extension UnorderedSparseSet: Equatable where UnorderedSparseSet.Element: Equatable {
+extension UnorderedSparseSet.Entry: Equatable where Element: Equatable { }
+extension UnorderedSparseSet: Equatable where Element: Equatable {
     public static func == (lhs: UnorderedSparseSet<Element>, rhs: UnorderedSparseSet<Element>) -> Bool {
         return lhs.dense == rhs.dense && lhs.sparse == rhs.sparse
     }
diff --git a/Tests/FirebladeECSTests/SingleTests.swift b/Tests/FirebladeECSTests/SingleTests.swift
index 141934d..fd5eda0 100644
--- a/Tests/FirebladeECSTests/SingleTests.swift
+++ b/Tests/FirebladeECSTests/SingleTests.swift
@@ -56,4 +56,12 @@ class SingleTests: XCTestCase {
         XCTAssertEqual(single.component.playerHealth, gameState.playerHealth)
         
     }
+    
+    func testSingleCreationOnExistingFamilyMember() {
+        _ = nexus.create(entity: "AnotherEntity", with: Position(x: 1, y: 2))
+        let singleGame = SingleGameState()
+        _ = nexus.create(entity: "CrashEntity", with: singleGame)
+        let single = nexus.single(SingleGameState.self)
+        XCTAssertTrue(singleGame === single.component)
+    }
 }
diff --git a/Tests/FirebladeECSTests/SparseSetTests.swift b/Tests/FirebladeECSTests/SparseSetTests.swift
index 6c8c509..ff66583 100644
--- a/Tests/FirebladeECSTests/SparseSetTests.swift
+++ b/Tests/FirebladeECSTests/SparseSetTests.swift
@@ -500,8 +500,8 @@ class SparseSetTests: XCTestCase {
 
         XCTAssertEqual(characters.count, 11)
 
-        let string: String = characters.reduce("") { res, char in
-            res + "\(char)"
+        let string: String = characters.dense.reduce("") { res, char in
+            res + "\(char.element)"
         }
 
         // NOTE: this tests only dense insertion order, this is no guarantee for the real ordering.
@@ -539,4 +539,17 @@ class SparseSetTests: XCTestCase {
         XCTAssertEqual(characters[34], "l")
         XCTAssertEqual(characters[140], "d")
     }
+    
+    func testStartEndIndex() {
+        
+        let set = UnorderedSparseSet<Character>()
+        
+        set.insert("C", at: 33)
+        set.insert("A", at: 11)
+        set.insert("B", at: 22)
+        
+        let mapped = set.dense.map { $0.element }
+        
+        XCTAssertEqual(mapped, ["C", "A", "B"])
+    }
 }