This looks to be because there is a different approach to how our Font Awesome icons load in Presentation vs the Authoring Panel. The best fix is for me to update the hard-coded icons inside the Family Tree widget to use the newer version of FA's naming (this widget was built on version 4, and we're now on version 7 lol. 5 and 6 had changed some names around to be more consistent, so it's not a surprise that it has bugged like this. Had to fix it in Plato too, before we deprecated that editor)
I'll take a look at this and test a fix when I have some time, and then I'll update this issue.