Monica’s relationship with her parents was often a contentious one on Friends, but the reason might be because she’s the love child of Judy and another man. Friends made its debut on NBC in 1994 and came to an end in 2004 after 10 seasons and a lot of ups and downs in the lives of Monica, Rachel, Phoebe, Chandler, Joey, and Ross.

All six friends came from different backgrounds and represented different types of families – Phoebe was adopted and later became an orphan, both Chandler and Rachel’s parents were divorced (under very different circumstances), and Ross and Monica’s parents were still together, but they didn’t treat their children equally. Both Jack and Judy always favored Ross, but Jack had some father-and-daughter moments with Monica throughout the series. Judy, on the other hand, was always very harsh towards Monica.

Monica was very patient when it came to her mother (for the most part, as she understandably snapped a couple of times), but Judy almost never changed her attitude towards her – and it might have been because she was hiding something.

Theory: Monica Wasn’t Jack’s Daughter

This theory originated on Reddit, although the original post is now gone. The Friends theory suggests that the reason for Judy’s rudeness towards her daughter is that Monica was the love child of an extra-marital affair of Judy’s. Every time she saw Monica, she was reminded of that bad decision and was overcome with shame (and fear), and took it all out on her. The theory even suggested that Monica’s real dad wasn’t Jewish, which would explain why Ross was more into his Jewish roots than Monica.

However, the theory could go the other way around, with Monica not being Judy’s daughter. Jack could have had an affair and the result was Monica. What happened to her “real mother” is unknown, but Monica not being Judy’s daughter can explain why she favored Ross so much. Monica was a reminder of Jack’s infidelity, and that’s why Judy was constantly criticizing, shaming, and even humiliating her. The relationship between Judy and Monica was one of the toughest ones to watch, mostly because Judy never changed her attitude towards her (she had one or two moments in which she acknowledged her hard work, but they were very brief and rare). Friends never explored why Judy acted like that, but this theory (and its variant) fits so well it could be the explanation viewers never got.

Next: Friends’ Original Chandler Plan Would’ve Killed The Show