can the main html tag have other siblings code example

Example 1: css select all siblings after element

/*To match to any sibling element after the selector on the left,
  use the tilde symbol '~'. This is called the general sibling combinator. */

h1 ~ p {
  color: black;
}

Example 2: sibling selector css

/*General Sibling*/
/*The general sibling selector selects all elements that are siblings of a specified element.
The following example selects all <p> elements that are siblings of <div> elements: */
/*<div></div>
  <p></p>*/
div ~ p{
}

/*Adjacent Sibling*/
/*The adjacent sibling selector is used to select an element that is directly after another specific element.
Sibling elements must have the same parent element, and "adjacent" means "immediately following".
The following example selects the first <p> element that are placed immediately after <div> elements*/
/*<div><p></p></div>
  */
div + p{
}