In addition to being correlated in space, clusters are also correlated
in time.
Efremov &
Elmegreen (1998)
found that the age difference between clusters in
the LMC increases with the spatial separation as a
power-law, age 
separation1/2.
Elmegreen &
Efremov (1996)
found the same
age-separation correlation for Cepheid variables in the LMC.
de la Fuente Marcos
& de la Fuente Marcos (2009a)
showed that this correlation also applies to clusters in
the solar neighborhood. In both cases, the correlation is strongest for
young clusters with a separation less than ~ 1 kpc, and it goes
away for older clusters. Presumably the young clusters follow the
correlated structure that the gas had when the clusters formed.
Clusters form faster in regions with higher densities out to a kpc or
so, which is probably the ISM Jeans length. This means that small
star-forming regions (e.g., cluster cores) come and go during the life
of a larger star-forming region (an OB association), and then the
larger regions come and go during the life of an even larger region (a
star complex). Eventually, the clusters, associations and complexes
disperse when they age, taking more random positions after ~ 100
Myr. The correlation is about the same as the size-linewidth relation
for molecular clouds
(Larson 1981),
considering that the ratio of the size to the linewidth is a timescale.
Correlated star formation implies that some clusters should form in pairs. Cluster pairs were discovered in the LMC by Bhatia & Hatzidimitriou (1988) and in the SMC by Hatzidimitriou & Bhatia (1990). An example is the pair NGC 3293 and NGC 3324 near eta Carinae. de la Fuente Marcos & de la Fuente Marcos (2009b) studied these and other pairs. For NGC 3292/3324, the clusters are apparently weakly interacting and the age difference is 4.7 My. NGC 659 and NGC 663 are also weakly interacting and the age difference is 19.1 My. Dieball et al. (2002) determined the distribution function of the number of cluster members per cluster group in the LMC. They found a statistical excess of clusters in pairs compared to the expectation from random groupings.