Don't know if this is actually possible, but it appears Liam is already starting to associate names with people!
Just now, Jen was holding Liam, and turned him to face Maeve and I, who were sitting on the couch. He wasn't looking anywhere in particular. Then, Jen said, "Hi, Papa!" and his eyes moved to focus on me. A moment later, she said, "Hi, big sister!" and he moved is eyes to focus on Maeve.
As I type this, Jen just tried the experiment again with Maeve, and again he moved his eyes and head to look at her!
How cool and amazing it is to witness child development!