JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <fieldset class="box">
        <legend>Title</legend>CONTENT
        <br/>test</fieldset>
    <fieldset class="box">
        <legend>Title</legend>CONTENT</fieldset>
    <fieldset class="box">
        <legend>Title</legend>CONTENT</fieldset>
</div>

CSS

.box {
    float:left;
    width:25%;
}

JavaScript

$(function () {
    var H = 0;
    $("div").each(function (i) {
        var h = $(".box").eq(i).height();
        if (h > H) H = h;
    });
    $(".box").height(H);
});