The important things to consider are twofold: Have you got a pollinator tree for them. Some apple and pear varieties are very picky about which others they will pollinate, so regardless of the bee population they still might not be getting through. Also, have the trees been properly dwarfed? The old saying "!You plant pears for heirs" has a lot of truth to it. Unless dwarfed some trees can take 15 years to fruit properly. Most modern trees are on dwarfing stock, which can sort this out, but proper fruiting may take a while.