JavaScript вставьте брата после

<!-- beforebegin -->
<p>
  <!-- afterbegin -->
  foo
  <!-- beforeend -->
</p>
<!-- afterend -->

var tempDiv = document.createElement('div');
paragraph.insertAdjacentElement('afterend', tempDiv);

// inserted div after end of paragraph tag
<p>
	foo
</p>
<div></div>
Obedient Oyster