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This depends on the type of fruit trees. Some trees will have problems with being near pecans, as the roots can interfere, both physically, and chemically with your other trees. Some roots can extend out to 100 feet or more. Sometimes it can be safe to plant within 50 or 60 feet, but this will depend on the trees you intend to plant.
This article will give you more information: https://www.gardeningknowhow.com/edible/nut-trees/pecan/pecan-tree-toxicity.htm