Adding Relationships to Patched Legacy Families

Is there a way to add a Sim into a family tree from the patch update, when those Sims are only portraits without data?

I would like to link my Dirk Dreamer to Darren and Darleen in the family tree, but it is a save prior to the legacy patch. Though I could create a new save file, I have too much time invested in this particular save, and starting a new would be a major logistic headache for such a minor tweak. Any ideas, or is starting a new save the only way?

Thanks!