{define twoColumns}
<div class="row">
  <div class="col-md-6">{block col1}{/block}</div>
  <div class="col-md-6">{block col2}{/block}</div>
</li>
{/define}

{extends #twoColumns}
{block col1}.. some complex template code ..{/block}
{block col1}.. some complex template code ..{/block}
{/}