Crab apple trees

Question

Do I have to plant 2 crab apples and if so how far apart can they be.

Answer 1

Crabapples, however, are bred for their flowers. Some varieties are sterile and do not set fruit no matter what pollen is available, but the Adams crabapple is self-fertile. Adams crabapple flowers set fruit when they are pollinated by other flowers of the same tree.
Plant the Adams crabapple in full sun in well-drained, acidic loam soil, either as a specimen or in small groups.
https://www.gardeningknowhow.com/ornamental/trees/crabapple/flowering-crabapple-trees.htm