Given that they play such a believable mother-daughter duo, some viewers have jumped to the assumption that they’re related in real life, but that’s simply not the case.
According to Allison’s Wikipedia page, her mother’s name is Margo Miller. And according to Melora’s, her two children are named Rory and Piper Quincy Jackson, whom she shares with her husband, British actor and author Gildart Jackson.
The Season 4 finale of A Million Little Things airs on Wednesday, May 18 at 10 pm PST on ABC.
Source: https://www.distractify.com/p/are-allison-miller-and-melora-hardin-related