Solution 1 :

On change event you should check the value of the selected option. Also to remove the attribute you can use .removeAttr().

Try the following way:

$(document).ready(function(){
  $('form input[name="spouseName"]').prop("disabled", true);
  $('form input[name="children"]').prop("disabled", true);

  $("form select").change(function(){
    if($(this).val() == 'Married'){
      $('form input[name="spouseName"]').removeAttr("disabled")
      $('form input[name="children"]').removeAttr("disabled")
    }
    else{
      $('form input[name="spouseName"]').prop("disabled", true);
      $('form input[name="children"]').prop("disabled", true);
    }
  });
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form>
  <select class="form-control" name="maritalStatus" id="maritalStatus">
    <option value="Married">Married</option>
    <option selected value="UnMarried">UnMarried</option>
    <option value="Male Widow">Male Widow</option>
    <option value="FeMale Widow">FeMale Widow</option>
    <option value="Divorcee">Divorcee</option>
  </select>
  <input type="text" class="form-control" name="spouseName" id="spouseName" aria-describedby="spName" placeholder="Spose Name">
  <input type="text" class="form-control" name="children" id="children" aria-describedby="childrens" placeholder="Children">
</form>

Solution 2 :

You can try your required solution with conditions. Please check below code

$(document).ready(function() {
  $('form input[name="spouseName"]').prop("disabled", true);
  $('form input[name="children"]').prop("disabled", true);
  $("#maritalStatus").change(function() {
  		if($(this).val() !=='UnMarried'){
  	        $('form input[name="spouseName"]').prop("disabled", false);
           $('form input[name="children"]').prop("disabled", false);		
  		}else{
  			$('form input[name="spouseName"]').prop("disabled", true);
            $('form input[name="children"]').prop("disabled", true);
  		}
  });
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form>
  <select class="form-control" name="maritalStatus" id="maritalStatus">
    <option value="Married">Married</option>
    <option selected value="UnMarried">UnMarried</option>
    <option value="Male Widow">Male Widow</option>
    <option value="FeMale Widow">FeMale Widow</option>
    <option value="Divorcee">Divorcee</option>
  </select>
  <input type="text" class="form-control" name="spouseName" id="spouseName" aria-describedby="spName" placeholder="Spose Name">
  <input type="text" class="form-control" name="children" id="children" aria-describedby="childrens" placeholder="Children">
</form>

Solution 3 :

The “on change” event is related to the select and not the option

So you have to work with “if … else” in the both cases of values in the select whether “married” or not

Thus i make this change in your code and it works properly

$(document).ready(function() {
  $('form input[name="spouseName"]').prop("disabled", true);
  $('form input[name="children"]').prop("disabled", true);
  $("form select").change(function() {
  	if(this.value === 'Married'){
  		$('form input[name="spouseName"]').prop("disabled", false);
    	$('form input[name="children"]').prop("disabled", false);
  	}else{
  		$('form input[name="spouseName"]').prop("disabled", true);
  		$('form input[name="children"]').prop("disabled", true);
  	}    
  });
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<form>
  <select class="form-control" name="maritalStatus" id="maritalStatus">
    <option value="Married">Married</option>
    <option selected value="UnMarried">UnMarried</option>
    <option value="Male Widow">Male Widow</option>
    <option value="FeMale Widow">FeMale Widow</option>
    <option value="Divorcee">Divorcee</option>
  </select>
  <input type="text" class="form-control" name="spouseName" id="spouseName" aria-describedby="spName" placeholder="Spose Name">
  <input type="text" class="form-control" name="children" id="children" aria-describedby="childrens" placeholder="Children">
</form>

Solution 4 :

You didn’t mention whats not working but your onChange wont work.

The css selector has a space

option [value='married']

Should be:

option[value='married']

Problem :

I was using jquery 3.4.1 for this
I was trying to disable input elements when the different value selected.

$(document).ready(function() {
  $('form input[name="spouseName"]').prop("disabled", true);
  $('form input[name="children"]').prop("disabled", true);
  $("form select option [value='married']").change(function() {
    $('form input[name="spouseName"]').prop("disabled", false);
    $('form input[name="children"]').prop("disabled", false);
  });
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<form>
  <select class="form-control" name="maritalStatus" id="maritalStatus">
    <option value="Married">Married</option>
    <option selected value="UnMarried">UnMarried</option>
    <option value="Male Widow">Male Widow</option>
    <option value="FeMale Widow">FeMale Widow</option>
    <option value="Divorcee">Divorcee</option>
  </select>
  <input type="text" class="form-control" name="spouseName" id="spouseName" aria-describedby="spName" placeholder="Spose Name">
  <input type="text" class="form-control" name="children" id="children" aria-describedby="childrens" placeholder="Children">
</form>

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