After Charlie and Mac talk to Dee (Kaitlin Olson) and Dennis (Glenn Howerton) about what they might get from their parents when they die, Charlie and Mac decide to dig into their family history. Charlie claims that his fortune will come from his family teeth, but his mom already gave the teeth to his sisters. Yes, this is the first we’re hearing of Charlie’s sisters and they are as unhinged as we would expect.

When Mac asks his mom if there’s anything in their family history, even something sentimental, his mom reveals (in one-word spurts, of course) that his Uncle Donald has some letters written by his grandfather during the war. Mac decides to hijack Charlie’s trip to his sisters and stop in Hamburg, New Jersey to visit his Uncle Donald and get the letters.

Uncle Donald’s place seems surprisingly normal, considering what we know about Mac’s family. Mac’s father, Luther, is a convict who’s always on the wrong side of luck, and Mac’s mother is abusive and practically the opposite of maternal. Uncle Donald is perfectly nice, but strangely familiar. He shares how the letters were actually written to Mac’s father, Luther, and Donald was just holding onto them.

This is because Donald and Luther’s father, Mac’s grandfather, preferred Luther. He said that Donald was the “weird” one. Throughout Donald’s anecdote, it’s heavily hinted that Donald, like Mac, is gay, which is why he never got married or had children. Although Charlie picks up on this, Mac is oblivious and even says that he can’t relate to Donald’s challenges.

In fact, Donald offers to be like the father Mac never had. Mac is constantly seeking out his father’s approval to the point of pushing his father over the edge and creating a further rift between them. So when Donald offers to be Mac’s father figure, Charlie tries to help Mac make the connection, but Mac is his classic one-track-minded self who often misses the forest through the trees.