Image gets really small when I put it in a column - html

Question

My png images gets really small when I put them inside a column in a row. However they are fine when there is not column but then they do not appear as a row and appear one above the other. I have no idea what may be causing the problem.
What I want to do: I want them to appear like this.
<div class="container">
<div class="row" id="parent">
<div class="col-xs-4 col-sm-4 col-md-4 col-lg-4 block left">
<div class="heading">
<h3> Simple to Enjoy </h3>
</div>
<div class="inside">
<div class="row">
<div class=""> <!--These Images!!!-->
<img class="img img-responsive img-sec-4" src="images\home_section_4_free_ride.png">
<p>Free Rides </p>
</div>
<div class="">
<img class="img img-responsive img-sec-4" src="images\home_section_4_membership.png">
<p>Free XXX Membership </p>
</div>
</div>
</div>
</div>
<div class="col-xs-4 col-sm-4 col-md-4 col-lg-4 block center">
<div class="heading">
<h3> Simple to Earn </h3>
</div>
<div class="inside">
</div>
</div>
<div class="col-xs-4 col-sm-4 col-md-4 col-lg-4 block right">
<div class="heading">
<h3> Simple to Save </h3>
</div>
<div class="inside">
</div>
</div>
</div>
</div>
Sorry for bad english and indent.
Here is my CSS:
#parent {
text-align:center;
height:400px;
width:100%;
}
.center {
margin:auto
}
.left {
margin:auto auto auto 0;
}
.right {
margin:auto 0 auto auto;
}
.img-sec-4 {
height: auto;
width: auto;
}
EDIT:
Here is the screenshot of my result:
(The red highlighted area is where the problem is)

Answer 1

simply add class col-xs-6 to the div wrapping those images (each one)
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet"/>
<div class="container">
<div class="row" id="parent">
<div class="col-xs-4 col-sm-4 col-md-4 col-lg-4 block left">
<div class="heading">
<h3> Simple to Enjoy </h3>
</div>
<div class="inside">
<div class="row">
<div class="col-xs-6">
<!--These Images!!!-->
<img class="img img-responsive img-sec-4" src="//lorempixel.com/200/200">
<p>Free Rides</p>
</div>
<div class="col-xs-6">
<img class="img img-responsive img-sec-4" src="//lorempixel.com/200/200">
<p>Free XXX Membership</p>
</div>
</div>
</div>
</div>
<div class="col-xs-4 col-sm-4 col-md-4 col-lg-4 block center">
<div class="heading">
<h3> Simple to Earn </h3>
</div>
<div class="inside">
</div>
</div>
<div class="col-xs-4 col-sm-4 col-md-4 col-lg-4 block right">
<div class="heading">
<h3> Simple to Save </h3>
</div>
<div class="inside">
</div>
</div>
</div>
</div>