Arrange 2 items per row using flexbox

Imagine I have following markup

<div class="container">
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
    <div class="item"></div>
</div>

and style

.item {
  width: 100%
}

and due to certain reasons I can't change the width of the .item Can I arrange 2 items in each row by styling parent container .container, using flexbox or any other way?

You can give flex: 50% to children divs without touching .item

.item {
  width: 100%
}

.container {
  display: flex;
  flex-wrap: wrap;
}

.container > div {
  flex: 50%; /* or - flex: 0 50% - or - flex-basis: 50% - */
  /*demo*/
  box-shadow: 0 0 0 1px black;
  margin-bottom: 10px;
}

<div class="container">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item">4</div>
</div>

The below solution worked for me

.parent{
  display: flex;
  flex-wrap: wrap;
}

.child{
  width: 25%;
  box-sizing: border-box;
}

Sample: https://codepen.io/capynet/pen/WOPBBm