diff --git a/gtsam/hybrid/HybridGaussianConditional.cpp b/gtsam/hybrid/HybridGaussianConditional.cpp
index e0ae16e82..c31a9836f 100644
--- a/gtsam/hybrid/HybridGaussianConditional.cpp
+++ b/gtsam/hybrid/HybridGaussianConditional.cpp
@@ -78,21 +78,6 @@ HybridGaussianConditional::HybridGaussianConditional(
                                 DiscreteKeys{discreteParent},
                                 Conditionals({discreteParent}, conditionals)) {}
 
-/* *******************************************************************************/
-// TODO(dellaert): This is copy/paste: HybridGaussianConditional should be
-// derived from HybridGaussianFactor, no?
-GaussianFactorGraphTree HybridGaussianConditional::add(
-    const GaussianFactorGraphTree &sum) const {
-  using Y = GaussianFactorGraph;
-  auto add = [](const Y &graph1, const Y &graph2) {
-    auto result = graph1;
-    result.push_back(graph2);
-    return result;
-  };
-  const auto tree = asGaussianFactorGraphTree();
-  return sum.empty() ? tree : sum.apply(tree, add);
-}
-
 /* *******************************************************************************/
 GaussianFactorGraphTree HybridGaussianConditional::asGaussianFactorGraphTree()
     const {
diff --git a/gtsam/hybrid/HybridGaussianConditional.h b/gtsam/hybrid/HybridGaussianConditional.h
index 434750bc9..5c3e500bd 100644
--- a/gtsam/hybrid/HybridGaussianConditional.h
+++ b/gtsam/hybrid/HybridGaussianConditional.h
@@ -108,8 +108,9 @@ class GTSAM_EXPORT HybridGaussianConditional
                             const Conditionals &conditionals);
 
   /**
-   * @brief Make a Hybrid Gaussian Conditional from a vector of Gaussian conditionals.
-   * The DecisionTree-based constructor is preferred over this one.
+   * @brief Make a Hybrid Gaussian Conditional from a vector of Gaussian
+   * conditionals. The DecisionTree-based constructor is preferred over this
+   * one.
    *
    * @param continuousFrontals The continuous frontal variables
    * @param continuousParents The continuous parent variables
@@ -233,14 +234,6 @@ class GTSAM_EXPORT HybridGaussianConditional
    */
   void prune(const DecisionTreeFactor &discreteProbs);
 
-  /**
-   * @brief Merge the Gaussian Factor Graphs in `this` and `sum` while
-   * maintaining the decision tree structure.
-   *
-   * @param sum Decision Tree of Gaussian Factor Graphs
-   * @return GaussianFactorGraphTree
-   */
-  GaussianFactorGraphTree add(const GaussianFactorGraphTree &sum) const;
   /// @}
 
  private: