diff --git a/Sources/FirebladeECS/Nexus+Family.swift b/Sources/FirebladeECS/Nexus+Family.swift
index 0f5bd91..b7f096e 100644
--- a/Sources/FirebladeECS/Nexus+Family.swift
+++ b/Sources/FirebladeECS/Nexus+Family.swift
@@ -39,86 +39,3 @@ public extension Nexus {
 		return members.contains(entityId.index)
 	}
 }
-
-// MARK: - internal extensions
-extension Nexus {
-	internal func update(familyMembership entityId: EntityIdentifier) {
-		// FIXME: iterating all families is costly for many families
-        familyMembersByTraits.forEach { familyTraits, _ in update(membership: familyTraits, for: entityId) }
-	}
-
-    internal enum UpdateState {
-        case noComponents(id: EntityIdentifier, traits: FamilyTraitSet)
-        case added(id: EntityIdentifier, traits: FamilyTraitSet)
-        case removedDeleted(id: EntityIdentifier, traits: FamilyTraitSet)
-        case removed(id: EntityIdentifier, traits: FamilyTraitSet)
-        case unchanged(id: EntityIdentifier, traits: FamilyTraitSet)
-    }
-
-	internal func update(membership traits: FamilyTraitSet, for entityId: EntityIdentifier) {
-		let entityIdx: EntityIndex = entityId.index
-		guard let componentIds: SparseComponentIdentifierSet = componentIdsByEntity[entityIdx] else {
-            // no components - so skip
-            return
-		}
-
-        let isMember: Bool = self.isMember(entity: entityId, inFamilyWithTraits: traits)
-		if !exists(entity: entityId) && isMember {
-            remove(entityWithId: entityId, andIndex: entityIdx, fromFamilyWithTraits: traits)
-			return
-		}
-
-        // TODO: get rid of set creation for comparison
-		let componentsSet = ComponentSet(componentIds)
-		let isMatch: Bool = traits.isMatch(components: componentsSet)
-
-		switch (isMatch, isMember) {
-		case (true, false):
-            add(entityWithId: entityId, andIndex: entityIdx, toFamilyWithTraits: traits)
-			notify(FamilyMemberAdded(member: entityId, toFamily: traits))
-            return
-
-		case (false, true):
-            remove(entityWithId: entityId, andIndex: entityIdx, fromFamilyWithTraits: traits)
-			notify(FamilyMemberRemoved(member: entityId, from: traits))
-            return
-
-		default:
-			return
-		}
-	}
-
-    /// will be called on family init defer
-    internal func onFamilyInit(traits: FamilyTraitSet) {
-        if familyMembersByTraits[traits] == nil {
-            familyMembersByTraits[traits] = UniformEntityIdentifiers()
-        }
-
-        // FIXME: this is costly for many entities
-        for entity: Entity in entityStorage {
-            update(membership: traits, for: entity.identifier)
-        }
-    }
-
-    internal func onFamilyDeinit(traits: FamilyTraitSet) {
-        // nothing todo here
-    }
-}
-
-// MARK: - fileprivate extensions
-private extension Nexus {
-	final func calculateTraitEntityIdHash(traitHash: FamilyTraitSetHash, entityIdx: EntityIndex) -> TraitEntityIdHash {
-		return hash(combine: traitHash, entityIdx)
-	}
-
-	final func add(entityWithId entityId: EntityIdentifier, andIndex entityIdx: EntityIndex, toFamilyWithTraits traits: FamilyTraitSet) {
-        if familyMembersByTraits[traits] == nil {
-            familyMembersByTraits[traits] = UniformEntityIdentifiers()
-        }
-		familyMembersByTraits[traits]?.insert(entityId, at: entityIdx)
-	}
-
-	final func remove(entityWithId entityId: EntityIdentifier, andIndex entityIdx: EntityIndex, fromFamilyWithTraits traits: FamilyTraitSet) {
-		familyMembersByTraits[traits]?.remove(at: entityIdx)
-	}
-}
diff --git a/Sources/FirebladeECS/Nexus+FamilyUpdate.swift b/Sources/FirebladeECS/Nexus+FamilyUpdate.swift
new file mode 100644
index 0000000..a5bf3e4
--- /dev/null
+++ b/Sources/FirebladeECS/Nexus+FamilyUpdate.swift
@@ -0,0 +1,75 @@
+//
+//  Nexus+FamilyUpdate.swift
+//  FirebladeECS
+//
+//  Created by Christian Treffs on 14.02.19.
+//
+
+extension Nexus {
+    /// will be called on family init
+    final func onFamilyInit(traits: FamilyTraitSet) {
+        guard familyMembersByTraits[traits] == nil else {
+            return
+        }
+
+        familyMembersByTraits[traits] = UniformEntityIdentifiers()
+        update(familyMembership: traits)
+    }
+
+    final func update(familyMembership traits: FamilyTraitSet) {
+        // FIXME: iterating all entities is costly for many entities
+        for entity: Entity in entityStorage {
+            update(membership: traits, for: entity.identifier)
+        }
+    }
+
+    final func update(familyMembership entityId: EntityIdentifier) {
+        // FIXME: iterating all families is costly for many families
+        for (traits, _) in familyMembersByTraits {
+            update(membership: traits, for: entityId)
+        }
+    }
+
+    final func update(membership traits: FamilyTraitSet, for entityId: EntityIdentifier) {
+        let entityIdx: EntityIndex = entityId.index
+        guard let componentIds: SparseComponentIdentifierSet = componentIdsByEntity[entityIdx] else {
+            // no components - so skip
+            return
+        }
+
+        let isMember: Bool = self.isMember(entity: entityId, inFamilyWithTraits: traits)
+        if !exists(entity: entityId) && isMember {
+            remove(entityWithId: entityId, andIndex: entityIdx, fromFamilyWithTraits: traits)
+            return
+        }
+
+        // TODO: get rid of set creation for comparison by conforming UnorderedSparseSet to SetAlgebra
+        let componentsSet = ComponentSet(componentIds)
+        let isMatch: Bool = traits.isMatch(components: componentsSet)
+
+        switch (isMatch, isMember) {
+        case (true, false):
+            add(entityWithId: entityId, andIndex: entityIdx, toFamilyWithTraits: traits)
+            notify(FamilyMemberAdded(member: entityId, toFamily: traits))
+            return
+
+        case (false, true):
+            remove(entityWithId: entityId, andIndex: entityIdx, fromFamilyWithTraits: traits)
+            notify(FamilyMemberRemoved(member: entityId, from: traits))
+            return
+
+        default:
+            return
+        }
+    }
+
+    final func add(entityWithId entityId: EntityIdentifier, andIndex entityIdx: EntityIndex, toFamilyWithTraits traits: FamilyTraitSet) {
+        precondition(familyMembersByTraits[traits] != nil)
+        familyMembersByTraits[traits].unsafelyUnwrapped.insert(entityId, at: entityIdx)
+    }
+
+    final func remove(entityWithId entityId: EntityIdentifier, andIndex entityIdx: EntityIndex, fromFamilyWithTraits traits: FamilyTraitSet) {
+        precondition(familyMembersByTraits[traits] != nil)
+        familyMembersByTraits[traits].unsafelyUnwrapped.remove(at: entityIdx)
+    }
+}