{% assign n_cards = 0 %}

{% assign section_parent = include.url | remove:'index.html' %}

{% for page in site.pages %}

{% comment %}
Iterate over the pages under the parent
{% endcomment %}
{% assign checkArray = page.url | split:section_parent %}

{% if checkArray[0] == "" %}

{% capture n_cards %}{{ n_cards | plus:1 }}{% endcapture %}

{% endif %}

{% endfor %}

{{ n_cards }}