Yamato and Musashi are rivals. Their back-and-forth banter, in which they are very candid about their dislike for the other, has revealed that they knew each other when they were young. Many fans have speculated that the two women were once friends. This theory would be logical, as since both women clearly knew each other and both women chose to join Team Rocket, it would make sense that Yamato, as was the case with Musashi, had at least one parent who was a Team Rocket Agent. In a Battle Frontier episode, Takeshi falls for Yamato who is disguised as Nurse Joy, but senses something wrong with her due to his innate knowledge of the Joys. (Source: Wikipedia, edited)