html - Bootstrap 3: How to get two form inputs on one line and other inputs on individual lines?

Question

I trying to format my registration page with Bootstrap 3.1.1. I would like the first two inputs to be on the same line while the other inputs are one there own line. I have played around with the bootstrap classes "row", "form-inline", and "form-horizontal" to no avail.

Does anybody know how to do it?

Here is the Fiddle

<style>
.reg_name {
 max-width:200px;
}
</style>


<form name="registration_form" id='registration_form' class="form-inline">

        <div class="form-group">
            <label for="firstname" class="sr-only"></label>
            <input id="firstname" class="form-control input-group-lg reg_name" type="text" name="firstname"
                   title="Enter first name"
                   placeholder="First name"/>
        </div>

        <div class="form-group">
            <label for="lastname" class="sr-only"></label>
            <input id="lastname" class="form-control input-group-lg reg_name" type="text" name="lastname"
                   title="Enter last name"
                   placeholder="Last name"/>
        </div>

    <div class="form-group">
        <label for="username" class="sr-only"></label>
        <input id="username" class="form-control input-group-lg" type="text" autocapitalize='off' name="username"
               title="Enter username"
               placeholder="Username"/>
    </div>

    <div class="form-group">
        <label for="password" class="sr-only"></label>
        <input id="password" class="form-control input-group-lg" type="password" name="password"
               title="Enter password"
               placeholder="Password"/>
    </div>

 </form>

Answer 1

Use <div class="row"> and <div class="form-group col-xs-6">

Here a fiddle :https://jsfiddle.net/core972/SMkZV/2/