childVal = parseInt($('#pageSearch-children').val());
adultVal = parseInt($('#pageSearch-adults').val());
minValueChild = parseInt($('#pageSearch-children').attr('min'));
maxValueChild = parseInt($('#pageSearch-children').attr('max'));
minValueAdult = parseInt($('#pageSearch-adults').attr('min'));
maxValueAdult = parseInt($('#pageSearch-adults').attr('max'));
maxAbsolute = parseInt(( maxValueChild + maxValueAdult ) / 2);
combinedValueNumber = parseInt(adultVal + childVal);
if (combinedValueNumber < maxAbsolute) {
    $('.add').click(function() {
      if (childVal < maxValueChild) {
        $('#pageSearch-children').val(function(i, oldval) {
          return ++oldval;
        });
        childVal = $('#pageSearch-children').val();
      }
    });
    $('.sub').click(function() {
      if (childVal > minValueChild) {
        $('#pageSearch-children').val(function(i, oldval) {
          return --oldval;
        });
        childVal = $('#pageSearch-children').val();
      }
    });

    adultVal = $('#pageSearch-adults').val();
    minValueAdult = $('#pageSearch-adults').attr('min');
    maxValueAdult = $('#pageSearch-adults').attr('max');
    $('.add2').click(function() {
      if (adultVal < maxValueAdult) {
        $('#pageSearch-adults').val(function(i, oldval) {
          return ++oldval;
        });
        adultVal = $('#pageSearch-adults').val();
      }
    });
    $('.sub2').click(function() {
      if (adultVal > minValueAdult) {
        $('#pageSearch-adults').val(function(i, oldval) {
          return --oldval;
        });
        adultVal = $('#pageSearch-adults').val();
      }
    });
}


<div id="field1" class="centered">
    <h3 class="white black">
        <input class="backgroundNoneInput" type="number" value="1" id="pageSearch-adults" name="adults" min="0" max="{{ $property->property_sleeps or '99' }}" readonly>
        Adults
    </h3>
    <button type="button" class="sub2 backgourndNoneButt faded">
        <span class="white fa fa-minus fa-2x faPlusMin" aria-hidden="true">
        </span>
    </button>
    <button type="button" class="add2 backgourndNoneButt">
        <span class="white fa fa-plus fa-2x faPlusMin" aria-hidden="true">
        </span>
    </button>
</div>
<div id="field2" class="centered">
    <h3 class="white black">
        <input class="backgroundNoneInput" type="number" value="0" id="pageSearch-children" name="children" min="0" max="{{ $property->property_sleeps or '99' }}" readonly>
        Children
    </h3>
    <button type="button" class="sub backgourndNoneButt faded">
        <span class="white fa fa-minus fa-2x faPlusMin" aria-hidden="true">
        </span>
    </button>
    <button type="button" class="add backgourndNoneButt">
        <span class="white fa fa-plus fa-2x faPlusMin" aria-hidden="true">
        </span>
    </button>
</div>