The 2 is attracted by the tenderness, the pacificity, the humility and the tolerance of the 9. The 9 is attracted by the enthusiasm, attention, energy, and affection of the 2. They both have excellent social, interpersonal and adaptive skills. Both do not like conflict or stress, and can form an affectionate, harmonious and loving relationship.
The main potential problem of this relationship will be a question of authority, because both are quite adaptable in nature, and somebody has to make the decisions, which will be most of the time taken by the 2, but not always. And the 9 will have a hard time being heard. The 2 can even become rather dominating over time, and begin to try to control the 9. To which he will respond with stubborn resistance in the form of aggressive passivity.