Very often the word used for naming a relationship type (or an event type or any kind of stuff) has to be taken in a specific meaning which is explained through the description field.

It would helpful for translators to have this description available as extracted comment which is displayed above the source string by Weblate.

Note that adding/modifying extracted comments (in contrast with context keys)  doesn't discard the existing translations, so this change is very soft for translators.
See https://www.gnu.org/software/gettext/manual/html_node/PO-Files.html for more details about "extracted comments" in PO translation files.