JSFiddle - React, Tailwind, and code Playground

HTML

<div class="large-4 columns">
    <label for="checkbox">
        <input type="checkbox" id="checkbox">co-applicant</label>
    <div class="large-12 columns">
        <input type="text" class="inputbox" required pattern="[a-zA-Z]+" placeholder="First name" disabled="disabled">
    </div>
    <div class="large-12 columns">
        <input type="text" class="inputbox" required pattern="[a-zA-Z]+" placeholder="Last name" disabled="disabled">
    </div>
    <div class="large-12 columns">
        <input type="email" class="inputbox" required placeholder="Email" disabled="disabled">
    </div>
</div>

JavaScript

$('#checkbox').on('change', function() {
    if (this.checked) {
        $(this).closest('div').find('input').removeAttr("disabled");
    }
});