diff --git a/src/emevo/analysis/tree.py b/src/emevo/analysis/tree.py
index 7003672..db955fc 100644
--- a/src/emevo/analysis/tree.py
+++ b/src/emevo/analysis/tree.py
@@ -15,7 +15,6 @@
 from numpy.typing import NDArray
 from pyarrow import Table
 
-
 datafield = functools.partial(dataclasses.field, compare=False, hash=False, repr=False)
 
 
@@ -165,8 +164,8 @@ def from_iter(
         iterator: Iterable[tuple[int, int] | tuple[int, int, dict]],
         root_idx: int = 0,
     ) -> Tree:
-        nodes = {}
         root = Node(index=root_idx, is_root=True)
+        nodes = {}
 
         for item in iterator:
             if len(item) == 2:
@@ -191,6 +190,7 @@ def from_iter(
                 root.add_child(node)
 
             node.sort_children()
+        nodes[root_idx] = root
         return Tree(root, nodes)
 
     @staticmethod
@@ -300,7 +300,7 @@ def split(node: Node, threshold: int) -> int:
                 return size
 
         size = split(self.root, min_group_size)
-        if size < min_group_size:
+        if size > 0:
             split_nodes[self.root.index] = SplitNode(size)
 
         for node_index in split_nodes:
@@ -344,6 +344,17 @@ def _split_reward_mean(
         split_edges = set()
         reward_keys_t = tuple(reward_keys)
 
+        def find_group_root(node: Node) -> int:
+            ancestor_idx = node.index
+            ancestor = node.parent
+            while (
+                ancestor is not None
+                and (ancestor.index, ancestor_idx) not in split_edges
+            ):
+                ancestor_idx = ancestor.index
+                ancestor = ancestor.parent
+            return ancestor_idx
+
         def find_maxdiff_edge(
             frozen_split_edges: frozenset[tuple[int, int]]
         ) -> tuple[float, Edge]:
@@ -352,8 +363,9 @@ def find_maxdiff_edge(
             for edge in self.all_edges():
                 if (edge.parent.index, edge.child.index) in split_edges:
                     continue
+                parent_root = find_group_root(edge.parent)
                 parent_size, parent_reward = compute_reward_mean(
-                    edge.parent,
+                    parent_root,
                     skipped_edges=frozen_split_edges,
                     reward_keys=reward_keys_t,
                 )
diff --git a/tests/test_tree.py b/tests/test_tree.py
index cac2c47..e49fb9a 100644
--- a/tests/test_tree.py
+++ b/tests/test_tree.py
@@ -21,6 +21,18 @@ def treedef() -> list[tuple[int, int]]:
     return [(1, 0), (4, 1), (3, 1), (5, 1), (9, 5), (8, 5), (2, 0), (6, 2), (7, 2)]
 
 
+@pytest.fixture
+def treedef_with_reward() -> list[tuple[int, int]]:
+    #     0
+    #    / \
+    #   1   2
+    #  /|\  |\
+    # 3 4 5 6 7
+    #     |\
+    #     8 9
+    return [(1, 0), (4, 1), (3, 1), (5, 1), (9, 5), (8, 5), (2, 0), (6, 2), (7, 2)]
+
+
 def test_from_iter(treedef: list[tuple[int, int]]) -> None:
     tree = Tree.from_iter(treedef, root_idx=-1)
     preorder = list(map(operator.attrgetter("index"), tree.traverse(preorder=True)))
@@ -34,41 +46,31 @@ def test_split(treedef: list[tuple[int, int]]) -> None:
     tree = Tree.from_iter(treedef)
     sp1 = tree.split(min_group_size=3)
     assert len(sp1) == 4
-    assert sp1[0] == 0
-    for idx in [1, 3, 4]:
-        assert sp1[idx] == 1
-    for idx in [2, 6, 7]:
-        assert sp1[idx] == 2
-    for idx in [5, 8, 9]:
-        assert sp1[idx] == 3
+    parents = [sn for sn in sp1.values() if sn.parent is None]
+    assert len(parents) == 1
+    assert sp1[0] == parents[0]
+    assert sp1[0].size == 1
+    assert list(sp1[0].children) == [1, 2]
+    assert sp1[1].size == 3
+    assert sp1[2].size == 3
+    assert sp1[5].size == 3
 
     sp2 = tree.split(min_group_size=4)
-    assert len(sp2) == 4
-    for idx in [0, 2, 6, 7]:
-        assert sp2[idx] == 0
-    for idx in [1, 3, 4, 5, 8, 9]:
-        assert sp2[idx] == 1
-
-
-def test_multilabel_split(treedef: list[tuple[int, int]]) -> None:
-    tree = Tree.from_iter(treedef)
-    lb1 = tree.multilabel_split(min_group_size=3)
-    assert len(lb1) == 4
-    assert list(sorted(lb1[0])) == [0]
-    assert list(sorted(lb1[1])) == [0, 1, 3, 4]
-    assert list(sorted(lb1[2])) == [0, 2, 6, 7]
-    assert list(sorted(lb1[3])) == [0, 1, 5, 8, 9]
+    assert len(sp2) == 2
+    assert sp2[0].size == 4, sp2
+    assert sp2[1].size == 6
 
 
 def test_from_table() -> None:
     table = pq.read_table(ASSET_DIR.joinpath("profile_and_rewards.parquet"))
     tree = Tree.from_table(table, 20)
     for root in tree.root.children:
-        assert root.index < 10
+        assert root.index <= 20
         assert root.birth_time is not None
         for node in root.traverse():
             assert node.birth_time is not None
 
-    data_dict = tree.as_datadict(split=10)
-    for key in ["unique_id", "label", "in-label-0", "in-label-1"]:
+    split = tree.split(min_group_size=10)
+    data_dict = tree.as_datadict(split)
+    for key in ["unique_id", "label"]:
         assert key in data_dict