diff --git a/templates/input/form-element-label.html.twig b/templates/input/form-element-label.html.twig
index ff59587..d8ec357 100644
--- a/templates/input/form-element-label.html.twig
+++ b/templates/input/form-element-label.html.twig
@@ -25,7 +25,7 @@
     title_display == 'invisible' and not (is_checkbox or is_radio) ? 'sr-only',
     required ? 'js-form-required',
     required ? 'form-required',
-    required ? 'required'
+    required and not (is_checkbox or is_radio) ? 'required'
   ]
 -%}
 {% if title is not empty and title_display == 'invisible' and (is_checkbox or is_radio) -%}
diff --git a/templates/input/form-element.html.twig b/templates/input/form-element.html.twig
index 8e2cbd7..eb9917e 100644
--- a/templates/input/form-element.html.twig
+++ b/templates/input/form-element.html.twig
@@ -57,11 +57,12 @@
     'js-form-item-' ~ name|clean_class,
     title_display not in ['after', 'before'] ? 'form-no-label',
     disabled == 'disabled' ? 'form-disabled',
-    is_form_group ? 'form-group',
     is_radio ? 'radio',
     is_checkbox ? 'checkbox',
+    is_single_checkbox ? 'checkbox-standalone',
     is_autocomplete ? 'form-autocomplete',
-    has_error ? 'error has-error'
+    has_error ? 'error has-error',
+    required ? 'required',
   ]
 %}{%
   set description_classes = [
@@ -70,6 +71,11 @@
     description_display == 'invisible' ? 'visually-hidden',
   ]
 %}
+
+{% if is_form_group %}
+  <div class="form-group">
+{% endif %}
+
 <div{{ attributes.addClass(classes) }}>
   {% if label_display in ['before', 'invisible'] %}
     {{ label }}
@@ -99,3 +105,7 @@
     </div>
   {% endif %}
 </div>
+
+{% if is_form_group %}
+  </div>
+{% endif %}
diff --git a/templates/system/fieldset.html.twig b/templates/system/fieldset.html.twig
new file mode 100644
index 0000000..c3dc235
--- /dev/null
+++ b/templates/system/fieldset.html.twig
@@ -0,0 +1,80 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a fieldset element and its children.
+ *
+ * Available variables:
+ * - attributes: HTML attributes for the <fieldset> element.
+ * - errors: (optional) Any errors for this <fieldset> element, may not be set.
+ * - required: Boolean indicating whether the <fieldset> element is required.
+ * - legend: The <legend> element containing the following properties:
+ *   - title: Title of the <fieldset>, intended for use as the text
+       of the <legend>.
+ *   - attributes: HTML attributes to apply to the <legend> element.
+ * - description: The description element containing the following properties:
+ *   - content: The description content of the <fieldset>.
+ *   - attributes: HTML attributes to apply to the description container.
+ * - description_display: Description display setting. It can have these values:
+ *   - before: The description is output before the element.
+ *   - after: The description is output after the element (default).
+ *   - invisible: The description is output after the element, hidden visually
+ *     but available to screen readers.
+ * - children: The rendered child elements of the <fieldset>.
+ * - prefix: The content to add before the <fieldset> children.
+ * - suffix: The content to add after the <fieldset> children.
+ *
+ * @see template_preprocess_fieldset()
+ *
+ * @ingroup themeable
+ */
+#}
+{%
+  set classes = [
+    'js-form-item',
+    'form-item',
+    'js-form-wrapper',
+    'form-wrapper',
+  ]
+%}
+<fieldset{{ attributes.addClass(classes) }}>
+  {%
+    set legend_span_classes = [
+      'field-name',
+      'fieldset-legend',
+      required ? 'js-form-required',
+      required ? 'form-required',
+    ]
+  %}
+  {%
+    set legend_classes = [
+      required ? 'required',
+    ]
+  %}
+  {# Always wrap fieldset legends in a <span> for CSS positioning. #}
+  <legend{{ legend.attributes.addClass(legend_classes) }}>
+    <span{{ legend_span.attributes.addClass(legend_span_classes) }}>{{ legend.title }}</span>
+    {% if required %}
+      <strong class="required">({{ 'required'|t }})</strong>
+    {% endif %}
+  </legend>
+  <div class="fieldset-wrapper">
+    {% if description_display == 'before' and description.content %}
+      <div{{ description.attributes.addClass('description') }}>{{ description.content }}</div>
+    {% endif %}
+    {% if errors %}
+      <div>
+        {{ errors }}
+      </div>
+    {% endif %}
+    {% if prefix %}
+      <span class="field-prefix">{{ prefix }}</span>
+    {% endif %}
+    {{ children }}
+    {% if suffix %}
+      <span class="field-suffix">{{ suffix }}</span>
+    {% endif %}
+    {% if description_display in ['after', 'invisible'] and description.content %}
+      <div{{ description.attributes.addClass('description') }}>{{ description.content }}</div>
+    {% endif %}
+  </div>
+</fieldset>
diff --git a/wxt_bootstrap.theme b/wxt_bootstrap.theme
index db40f02..bc0dc84 100644
--- a/wxt_bootstrap.theme
+++ b/wxt_bootstrap.theme
@@ -23,6 +23,7 @@
  * @see \Drupal\bootstrap\Registry
  */
 
+use Drupal\Component\Utility\Html;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\file\Entity\File;
 use Drupal\image\Entity\ImageStyle;
@@ -213,6 +214,29 @@ function wxt_bootstrap_preprocess_input(&$variables) {
   else {
     $variables['search_submit'] = 'false';
   }
+
+  // Only for checkboxes.
+  $type_attr = $variables['attributes']['type'] ?? NULL;
+  $type = $type_attr ? (string) $type_attr->value() : NULL;
+
+  if ($type == 'checkbox') {
+    // We need inputs that look like name="base[option]".
+    $name_attr = $variables['attributes']['name'] ?? NULL;
+    $name = $name_attr ? (string) $name_attr->value() : NULL;
+    if (!$name || !preg_match('/^([^\\[]+)\\[.+\\]$/', $name, $m)) {
+      return;
+    }
+
+    $base = $m[1];
+    // Build a stable, CSS-safe class per base name.
+    $group_class = 'js-wet-group-' . Html::getClass($base);
+    $selector = '.' . $group_class;
+
+    // Attach the shared class and the validation rule to every checkbox in the group.
+    $variables['attributes']->addClass($group_class);
+    $variables['attributes']->setAttribute('data-rule-require_from_group', '[1,"' . $selector . '"]');
+    $variables['attributes']->setAttribute('data-rule-required', 'false');
+  }
 }
 
 /**
@@ -338,3 +362,42 @@ function wxt_bootstrap_preprocess_paragraph(&$variables) {
     $variables['link_provider_label'] = $allowed_values[$key] ?? $key;
   }
 }
+
+/**
+ * Implements hook_preprocess_form_element().
+ */
+function wxt_bootstrap_preprocess_form_element(array &$variables) {
+  // Mirror #required from the render array to Twig's $required so the template
+  // can add required classes/markers (used by GCWeb/WET and legend styling).
+  if (!empty($variables['element']['#required'])) {
+    $variables['required'] = TRUE;
+  }
+
+  // Webform context: if this is the single "checkbox" plugin, force Bootstrap's
+  // form-group wrapper and flag it as a single checkbox so spacing/markup match
+  if (!empty($variables['element']['#webform_plugin_id'])) {
+    if ($variables['element']['#webform_plugin_id'] == 'checkbox') {
+      $variables['is_form_group'] = TRUE;
+      $variables['is_single_checkbox'] = TRUE;
+    }
+  }
+}
+
+/**
+ * Implements hook_preprocess_fieldset().
+ */
+function wxt_bootstrap_preprocess_fieldset(array &$variables) {
+  $element = $variables['element'] ?? [];
+  $checkbox_radio_group = [
+    'radios',
+    'checkboxes',
+  ];
+
+  // When the fieldset is a radios/checkboxes group, add a marker class so
+  // WET/GCWeb can style spacing/legend consistently.
+  if (in_array($element['#type'], $checkbox_radio_group)) {
+    if (isset($variables['attributes'])) {
+      $variables['attributes']['class'][] = 'chkbxrdio-grp';
+    }
+  }
+}