Relationship between type 4 and type 9

The artist and the peacemaker

Éponine (Les Misérables)
Frodo Baggins (LOTR)

Attraction

The 4 is attracted by tolerance, patience, appeasement, idealism and listening to 9.
The 9 is attracted by the compassion, passion, energy and emotional depth of 4.
Both are sensitive, friendly, empathic, romantic and like to find that in the other.
The 4 feels completely accepted by the 9th, so his fears of abandonment dissipate.
The 9 feels important with the attention of 4, and likes to be stimulated by his energy and his passion.

Points where to be careful

The 4 pays great attention to what he misses. And can begin to become more demanding and critical with the 9 with time. 9 gives unconditional acceptance, and wishes it back. The 4 wants excitement and intensity, while the 9 wants comfort. This causes a conflicting problem. The 4 can become dissatisfied with too much peace of mind and disappoint the 9 who will start locking on himself.
The 9 can see the 4 as being sometimes too demanding, egocentric, critical, dramatic and emotionally unstable.
The 4 may see the 9 as being too disorganized, lazy, irresponsible, inefficient, boring and stubborn.