diff --git a/tests/test_class_sh_disowning_mi.cpp b/tests/test_class_sh_disowning_mi.cpp
index a41b8dfea..86333e864 100644
--- a/tests/test_class_sh_disowning_mi.cpp
+++ b/tests/test_class_sh_disowning_mi.cpp
@@ -5,7 +5,7 @@
 #include <memory>
 
 namespace pybind11_tests {
-namespace wip {
+namespace class_sh_disowning_mi {
 
 // Diamond inheritance (copied from test_multiple_inheritance.cpp).
 struct B {
@@ -29,50 +29,35 @@ struct D : public C0, public C1 {
 
 void disown_b(std::unique_ptr<B>) {}
 
-const std::string fooNames[] = {"ShPtr_"};
-
-template <int SerNo>
-struct Foo {
-    std::string history;
-    explicit Foo(const std::string &history_) : history(history_) {}
-    Foo(const Foo &other) : history(other.history + "_CpCtor") {}
-    Foo(Foo &&other) noexcept : history(other.history + "_MvCtor") {}
-    Foo &operator=(const Foo &other) {
-        history = other.history + "_OpEqLv";
-        return *this;
-    }
-    Foo &operator=(Foo &&other) noexcept {
-        history = other.history + "_OpEqRv";
-        return *this;
-    }
-    std::string get_history() const { return "Foo" + fooNames[SerNo] + history; }
+// test_multiple_inheritance_python
+struct Base1 {
+    explicit Base1(int i) : i(i) {}
+    int foo() const { return i; }
+    int i;
 };
 
-using FooShPtr = Foo<0>;
+struct Base2 {
+    explicit Base2(int j) : j(j) {}
+    int bar() const { return j; }
+    int j;
+};
 
-} // namespace wip
+int disown_base1(std::unique_ptr<Base1> b1) { return b1->i * 2000 + 1; }
+int disown_base2(std::unique_ptr<Base2> b2) { return b2->j * 2000 + 2; }
+
+} // namespace class_sh_disowning_mi
 } // namespace pybind11_tests
 
-PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::wip::B)
-PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::wip::C0)
-PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::wip::C1)
-PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::wip::D)
+PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::class_sh_disowning_mi::B)
+PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::class_sh_disowning_mi::C0)
+PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::class_sh_disowning_mi::C1)
+PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::class_sh_disowning_mi::D)
 
-PYBIND11_TYPE_CASTER_BASE_HOLDER(pybind11_tests::wip::FooShPtr,
-                                 std::shared_ptr<pybind11_tests::wip::FooShPtr>)
+PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::class_sh_disowning_mi::Base1)
+PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::class_sh_disowning_mi::Base2)
 
 TEST_SUBMODULE(class_sh_disowning_mi, m) {
-    using namespace pybind11_tests::wip;
-
-    py::class_<FooShPtr, std::shared_ptr<FooShPtr>>(m, "FooShPtr")
-        .def("get_history", &FooShPtr::get_history);
-
-    m.def("test_ShPtr_copy", []() {
-        auto o = std::make_shared<FooShPtr>("copy");
-        auto l = py::list();
-        l.append(o);
-        return l;
-    });
+    using namespace pybind11_tests::class_sh_disowning_mi;
 
     py::classh<B>(m, "B")
         .def(py::init<>())
@@ -101,4 +86,10 @@ TEST_SUBMODULE(class_sh_disowning_mi, m) {
         });
 
     m.def("disown_b", disown_b);
+
+    // test_multiple_inheritance_python
+    py::classh<Base1>(m, "Base1").def(py::init<int>()).def("foo", &Base1::foo);
+    py::classh<Base2>(m, "Base2").def(py::init<int>()).def("bar", &Base2::bar);
+    m.def("disown_base1", disown_base1);
+    m.def("disown_base2", disown_base2);
 }
diff --git a/tests/test_class_sh_disowning_mi.py b/tests/test_class_sh_disowning_mi.py
index 8d3b3ea49..5f66e96b0 100644
--- a/tests/test_class_sh_disowning_mi.py
+++ b/tests/test_class_sh_disowning_mi.py
@@ -1,13 +1,249 @@
 from __future__ import annotations
 
+import pytest
+
 import env  # noqa: F401
 from pybind11_tests import class_sh_disowning_mi as m
 
 
-def test_disown_d():
+def test_diamond_inheritance():
+    # Very similar to test_multiple_inheritance.py:test_diamond_inheritance.
     d = m.D()
-    m.disown_b(d)
+    assert d is d.d()
+    assert d is d.c0()
+    assert d is d.c1()
+    assert d is d.b()
+    assert d is d.c0().b()
+    assert d is d.c1().b()
+    assert d is d.c0().c1().b().c0().b()
 
 
-def test_shptr_copy():
-    m.test_ShPtr_copy()
+def is_disowned(callable_method):
+    try:
+        callable_method()
+    except ValueError as e:
+        assert "Python instance was disowned" in str(e)  # noqa: PT017
+        return True
+    return False
+
+
+def test_disown_b():
+    b = m.B()
+    assert b.get() == 10
+    m.disown_b(b)
+    assert is_disowned(b.get)
+
+
+@pytest.mark.parametrize("var_to_disown", ["c0", "b"])
+def test_disown_c0(var_to_disown):
+    c0 = m.C0()
+    assert c0.get() == 1020
+    b = c0.b()
+    m.disown_b(locals()[var_to_disown])
+    assert is_disowned(c0.get)
+    assert is_disowned(b.get)
+
+
+@pytest.mark.parametrize("var_to_disown", ["c1", "b"])
+def test_disown_c1(var_to_disown):
+    c1 = m.C1()
+    assert c1.get() == 1021
+    b = c1.b()
+    m.disown_b(locals()[var_to_disown])
+    assert is_disowned(c1.get)
+    assert is_disowned(b.get)
+
+
+@pytest.mark.parametrize("var_to_disown", ["d", "c1", "c0", "b"])
+def test_disown_d(var_to_disown):
+    d = m.D()
+    assert d.get() == 10202130
+    b = d.b()
+    c0 = d.c0()
+    c1 = d.c1()
+    pytest.skip(
+        "BAKEIN_BREAK: Root cause for crashes in test_class_sh_shared_ptr_copy_move?"
+    )
+    m.disown_b(locals()[var_to_disown])
+    assert is_disowned(d.get)
+    assert is_disowned(c1.get)
+    assert is_disowned(c0.get)
+    assert is_disowned(b.get)
+
+
+# Based on test_multiple_inheritance.py:test_multiple_inheritance_python.
+class MI1(m.Base1, m.Base2):
+    def __init__(self, i, j):
+        m.Base1.__init__(self, i)
+        m.Base2.__init__(self, j)
+
+
+class B1:
+    def v(self):
+        return 1
+
+
+class MI2(B1, m.Base1, m.Base2):
+    def __init__(self, i, j):
+        B1.__init__(self)
+        m.Base1.__init__(self, i)
+        m.Base2.__init__(self, j)
+
+
+class MI3(MI2):
+    def __init__(self, i, j):
+        MI2.__init__(self, i, j)
+
+
+class MI4(MI3, m.Base2):
+    def __init__(self, i, j):
+        MI3.__init__(self, i, j)
+        # This should be ignored (Base2 is already initialized via MI2):
+        m.Base2.__init__(self, i + 100)
+
+
+class MI5(m.Base2, B1, m.Base1):
+    def __init__(self, i, j):
+        B1.__init__(self)
+        m.Base1.__init__(self, i)
+        m.Base2.__init__(self, j)
+
+
+class MI6(m.Base2, B1):
+    def __init__(self, i):
+        m.Base2.__init__(self, i)
+        B1.__init__(self)
+
+
+class B2(B1):
+    def v(self):
+        return 2
+
+
+class B3:
+    def v(self):
+        return 3
+
+
+class B4(B3, B2):
+    def v(self):
+        return 4
+
+
+class MI7(B4, MI6):
+    def __init__(self, i):
+        B4.__init__(self)
+        MI6.__init__(self, i)
+
+
+class MI8(MI6, B3):
+    def __init__(self, i):
+        MI6.__init__(self, i)
+        B3.__init__(self)
+
+
+class MI8b(B3, MI6):
+    def __init__(self, i):
+        B3.__init__(self)
+        MI6.__init__(self, i)
+
+
+@pytest.mark.xfail("env.PYPY")
+def test_multiple_inheritance_python():
+    # Based on test_multiple_inheritance.py:test_multiple_inheritance_python.
+    # Exercises values_and_holders with 2 value_and_holder instances.
+
+    mi1 = MI1(1, 2)
+    assert mi1.foo() == 1
+    assert mi1.bar() == 2
+
+    mi2 = MI2(3, 4)
+    assert mi2.v() == 1
+    assert mi2.foo() == 3
+    assert mi2.bar() == 4
+
+    mi3 = MI3(5, 6)
+    assert mi3.v() == 1
+    assert mi3.foo() == 5
+    assert mi3.bar() == 6
+
+    mi4 = MI4(7, 8)
+    assert mi4.v() == 1
+    assert mi4.foo() == 7
+    assert mi4.bar() == 8
+
+    mi5 = MI5(10, 11)
+    assert mi5.v() == 1
+    assert mi5.foo() == 10
+    assert mi5.bar() == 11
+
+    mi6 = MI6(12)
+    assert mi6.v() == 1
+    assert mi6.bar() == 12
+
+    mi7 = MI7(13)
+    assert mi7.v() == 4
+    assert mi7.bar() == 13
+
+    mi8 = MI8(14)
+    assert mi8.v() == 1
+    assert mi8.bar() == 14
+
+    mi8b = MI8b(15)
+    assert mi8b.v() == 3
+    assert mi8b.bar() == 15
+
+
+DISOWN_CLS_I_J_V_LIST = [
+    (MI1, 1, 2, None),
+    (MI2, 3, 4, 1),
+    (MI3, 5, 6, 1),
+    (MI4, 7, 8, 1),
+    (MI5, 10, 11, 1),
+]
+
+
+@pytest.mark.xfail("env.PYPY", strict=False)
+@pytest.mark.parametrize(("cls", "i", "j", "v"), DISOWN_CLS_I_J_V_LIST)
+def test_disown_base1_first(cls, i, j, v):
+    obj = cls(i, j)
+    assert obj.foo() == i
+    assert m.disown_base1(obj) == 2000 * i + 1
+    assert is_disowned(obj.foo)
+    assert obj.bar() == j
+    assert m.disown_base2(obj) == 2000 * j + 2
+    assert is_disowned(obj.bar)
+    if v is not None:
+        assert obj.v() == v
+
+
+@pytest.mark.xfail("env.PYPY", strict=False)
+@pytest.mark.parametrize(("cls", "i", "j", "v"), DISOWN_CLS_I_J_V_LIST)
+def test_disown_base2_first(cls, i, j, v):
+    obj = cls(i, j)
+    assert obj.bar() == j
+    assert m.disown_base2(obj) == 2000 * j + 2
+    assert is_disowned(obj.bar)
+    assert obj.foo() == i
+    assert m.disown_base1(obj) == 2000 * i + 1
+    assert is_disowned(obj.foo)
+    if v is not None:
+        assert obj.v() == v
+
+
+@pytest.mark.xfail("env.PYPY", strict=False)
+@pytest.mark.parametrize(
+    ("cls", "j", "v"),
+    [
+        (MI6, 12, 1),
+        (MI7, 13, 4),
+        (MI8, 14, 1),
+        (MI8b, 15, 3),
+    ],
+)
+def test_disown_base2(cls, j, v):
+    obj = cls(j)
+    assert obj.bar() == j
+    assert m.disown_base2(obj) == 2000 * j + 2
+    assert is_disowned(obj.bar)
+    assert obj.v() == v