Answer: Unfortunately, it sounds like the trees were planted without regard for their ultimate size and care. You might find the pruning information at the following site helpful for dealing with the fruit crop trees. At the very least, the descriptions of pruning cuts and timing should be helpful even though you do not necessarily want to maximize the fruit production.
( http://www.ces.ncsu.edu/depts/hort/hil/ag29.html )
Keep in mind that it may take two years or so to bring them back into shape, using a combination of summer and dormant pruning techniques. Also keep in mind that size is probably better controlled through use of a dwarfing rootstock than by pruning, so the trees may simply be too crowded. Ultimately too you might find it wise to remove several of the trees, but do this only after careful consideration as to the pollination needs of each.
You might also want to consult with your county extension as to the suggested spray routine needed to keep the trees healthy and producing well. This would be based on the specific variety of tree you have as well as the local incidences of diseases and pests as well as on the weather each year.
Finally, crabapple trees are not usually pruned as one would prune a fruit producer but instead are treated as ornamental trees and given a minimal amout of pruning only as needed to enhance their looks.
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