fixup! CLDC-4145: Derive is partner for under 16s

app/models/derived_variables/lettings_log_variables.rb

@@ -278,7 +278,9 @@ private
     (2..8).each do |idx|
       if public_send("age#{idx}_changed?")
         self["ecstat#{idx}"] = nil if self["ecstat#{idx}"] == 9
-        self["relat#{idx}"] = nil if self["relat#{idx}"] == "X" && form.start_year_2026_or_later?
+        # since the user can also input 'No' for relat there are cases when we don't want to clear this (changing age from 50 to 55 for example)
+        # note if age is changed from 10 to 15 we will clear it but the inference will set it back immediately after, see child_under_16_constraints!
+        self["relat#{idx}"] = nil if self["relat#{idx}"] == "X" && age_changed_from_below_16(idx) && form.start_year_2026_or_later?
       end
     end
   end

app/models/lettings_log.rb

@@ -407,6 +407,10 @@ class LettingsLog < Log
     public_send("age#{person_index}") && public_send("age#{person_index}") < 16
   end
 
+  def age_changed_from_below_16(person_index)
+    public_send("age#{person_index}") && public_send("age#{person_index}_was") < 16
+  end
+
   def is_shared_housing?
     # 4: Shared flat or maisonette
     # 9: Shared house