In The Rise of Skywalker we find out that the connection between Rey and Kylo is a bit more than what we first though. They form a dyad in the Force: a pairing of two physical beings that become one in the Force.
Kylo Ren: My mother was the daughter of Vader. Your father was the son of the Emperor. What Palpatine doesn’t know is we’re a dyad in the Force way. Two that are one. We’ll kill him together and take the throne.
The Rise of Skywalker
Later on we learn of a prophecy about this dyad in the Force that was about restoring Emperor Palpatine to his former self.
Emperor Palpatine: The life force of your bond, a dyad in the Force. A power like life itself. Unseen for generations. And now, the power of two restores the one true Emperor.
The Rise of Skywalker
What is interesting about this though is that Palpatine says "Unseen for generations" which indicates it has been seen before.
Do we know when a dyad in the Force has shown up before? If not have we seen any other Force-bonds similar to Rey and Kylo that could have been a dyad but it just wasn't named yet? (The Rise of Skywalker and its Visual Dictionary seem to be the first time it was identified as a dyad in the Force).
Legends answers are acceptable but I am mainly looking for canon answers.