JSFiddle - React, Tailwind, and code Playground

HTML

<form >             
   <input type="text" placeholder="First Name" required id="fname" name="fname"/>
   <input type="text" placeholder="Last Name" required id="lname" name="lname"/>

   <input type="checkbox" placeholder="Maiden Name" id="maidenname" name="chkname"/>

   <input type="text" placeholder="Maiden Name" id="mname" name="mname"/>
</form>

CSS

#mname {
    display:none;
}
#maidenname:checked ~ #mname {
    display:block;
}