Open: memberlist.php
Find:
, u.user_allow_pm
In-line Add after:
, u.user_gender

Open: styles/prosilver/template/memberlist_leaders.html
Find:
{group.user.USERNAME_FULL}
In-line Add after:
 {group.user.USER_GENDER}

Open: styles/subsilver2/template/memberlist_leaders.html
Find:
{group.user.USERNAME_FULL}</strong>
In-line Add after:
 {group.user.USER_GENDER}