Так
.radio-center > .mes-radio {}
.aaaform-control-wrap > .class-mes {}
Или так
.aaaform-control-wrap.mes-radio {}
.aaaradio.class-mes {}
Или сделать доп. класс(модификатор)
<div class="radio-center">
<span class="aaaform-control-wrap mes-radio mes-radio--wrap">
<span class="aaaform-control aaaradio class-mes class-mes--aaaradio" id="id-mes">
<span class="aaalist-item first">
<label><input type="radio" name="mes-radio" value="до года" checked=""><span class="aaalist-item-label">до года</span></label></span>
<span class="aaalist-item">
<label><input type="radio" name="mes-radio" value="1-3 лет"><span class="aaalist-item-label">1-3 лет</span></label></span>
<span class="aaalist-item">
<label><input type="radio" name="mes-radio" value="3-5 лет"><span class="aaalist-item-label">3-5 лет</span></label></span>
<span class="aaalist-item last">
<label><input type="radio" name="mes-radio" value="от 5 лет"><span class="aaalist-item-label">от 5 лет</span></label></span>
</span>
</span>
</div>
.mes-radio.mes-radio--wrap {}
.class-mes.class-mes--aaaradio{}