BUddypress Show Xprofile Field Data in The Profile Header Username.

yzc_add_xprofile_field_data_in_profile_header.php

<?php
/**
 * BUddypress Show Xprofile Field Data in The Profile Header Username.
 */
function yzc_add_xprofile_field_data_in_profile_header( $name ) {

    if ( bp_is_user() ) {
        $field_data = xprofile_get_field_data( 'Age', bp_displayed_user_id() );
        if ( ! empty( $field_data ) ) {
            return $name . ', <span class="bp-user-age">' . $field_data . '</span>';
        }
    }

    return $name;

}

add_action( 'bp_get_displayed_user_mentionname', 'yzc_add_xprofile_field_data_in_profile_header' );