Actually, this is not unusual because an attraction can take place on a biological level that isn't even recognized. They have discovered how this can take place even between a daughter and father that were estranged for many years that finally met only to get very confused by finding they both experienced a strong attraction towards each other that deeply confused both of them. Then when they reached out for help it was explained to them how this can happen where their bodies were picking up on the pheromones that they both had that were a match that they were not at all aware of.

https://en.wikipedia.org/wiki/Pheromone