coincidental
adj.happening at the same time by chance, not because one thing caused the other. You use this to describe two events that are not connected.
adj.occurring at the same time by chance or without any direct connection. Often used to describe events that appear related but are actually independent.
“It was a coincidental meeting at the park.”
“The two companies were founded on the same day, though their success was purely coincidental.”
“While the timing of the two events appeared suspiciously coincidental to the public, the investigators found no evidence of a prearranged plan.”
“Perhaps not coincidental to its history, Trastevere has long been Rome’s bohemian neighborhood.”
From co- + incidental.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.