If we plot one people on a graph, in the range of strength and weakness, it could well be a bell curve, assume the one has more skills at average level, but some of the skills will be at either side of long tail.
When two being put together, if they have samiliar set of strength and weakness, they will have a higher chance of resonate, strength becomes stronger, weakness becomes weaker.
However, when two has too much of distance in each other, it might end up with weaken the strength, reinforce the weaness.
This is more of static view, while the reality might be more dynamic in the long run.
The curves start where they are, but up to people to draw the future.