And allow for tweaking baby chance as well.

common/net/minecraftforge/common/ForgeDummyContainer.java

@@ -53,6 +53,7 @@ public class ForgeDummyContainer extends DummyModContainer implements WorldAcces
     public static boolean fullBoundingBoxLadders = false;
     public static double zombieSummonBaseChance = 0.1;
     public static int[] blendRanges = { 20, 15, 10, 5 };
+    public static float zombieBabyChance = 0.05f;
 
     public ForgeDummyContainer()
     {
@@ -149,6 +150,10 @@ public class ForgeDummyContainer extends DummyModContainer implements WorldAcces
         prop.comment = "Base zombie summoning spawn chance. Allows changing the bonus zombie summoning mechanic.";
         zombieSummonBaseChance = prop.getDouble(0.1);
         
+        prop = config.get(Configuration.CATEGORY_GENERAL, "zombieBabyChance", 0.05);
+        prop.comment = "Chance that a zombie (or subclass) is a baby. Allows changing the zombie spawning mechanic.";
+        zombieBabyChance = (float) prop.getDouble(0.05);
+        
         if (config.hasChanged())
         {
             config.save();

patches/minecraft/net/minecraft/entity/monster/EntityZombie.java.patch

@@ -17,3 +17,12 @@
      }
  
      protected void entityInit()
+@@ -442,7 +443,7 @@
+ 
+         if (par1EntityLivingData1 == null)
+         {
+-            par1EntityLivingData1 = new EntityZombieGroupData(this, this.worldObj.rand.nextFloat() < 0.05F, this.worldObj.rand.nextFloat() < 0.05F, (EntityZombieINNER1)null);
++            par1EntityLivingData1 = new EntityZombieGroupData(this, this.worldObj.rand.nextFloat() < 0.05F, this.worldObj.rand.nextFloat() < ForgeDummyContainer.zombieBabyChance, (EntityZombieINNER1)null);
+         }
+ 
+         if (par1EntityLivingData1 instanceof EntityZombieGroupData)