John - do you keep bees away from your meyers? if so, how?

Do you mean a citrus tree is incapable of pollinating itself if there are not any bees, and this is the reason there are no seeds?

Are there any citrus that actually require pollination to produce fruit? If so, what are some examples?

Pollination - the act of fertilizing flowers to create fruit or seed - requires some sort of activity, either via wind, insect pollinators or the grower/gardener. Citrus are often self fertile but that is not the same as self-pollinating.

A number of citrus species are parthenocarpic or have an ability to produce fruit without pollination. These are typically the varieties you see sold as "seedless" - naval oranges and some satsumas. Clementines and mandarin hybrids are generally not parthenocarpic and do require pollination. Other types of citrus may occasionally produce parthenocarpic fruit yet still produce some seeds

Ah yes, I have a rare pear variety, Passe Crassane, that is said to be parthenocarpic.

Are the majority of citrus varieties not parthenocarpic? Would Oroblanco be an example of parthenocarpy, or do its seeds just abort? (because I do see tiny underformed seeds in there)

Junk,

I do not try to keep bees away, nor do I try to attract them; although if there is a bee within a kilometer of a Meyer lemon flower, it will come. One of my projects is in an area surrounded by sugar cane plantations; and bees do not like sugar cane; those lemons are essentially seedless; and are nearly 80% juice by weight compared to our "normal" Meyers which are 70%. Note, the seeds are heavier than the lemon; which is why Argentina puts a lot of bees in their Eureka lemons.