I bought two holly (Ilex ) bushes about 19 years ago from Spenards Building Supply. Not a specialty nursery by any means, but a store that on and off has had great garden center managers. They have also had some pretty uninspired ones.
I'm pretty certain that the plants are Blue Girl and Blue Boy (Ilex x meserveae) a very hardy hybrid. The Blue boys and girls are hybrids of English holy (I. aquilfolium) and Ilex rugosa. Blue Boy is of course male flowered and Blue Girl, female flowered. These hollies like many of the oldest shrubs in my garden have moved a time or two. These have not been given the best or sunniest spot, they are slow growing and I was dubious about every seeing a berry. Their current home is on the east side of the house near the very small artificial pond. They get a reasonable amount of light, but little straight sun. The site has good drainage and acid soil, both conditions that this plant enjoys. There is shelter from the southeast wind.

Most years I've given the hollies the same fertilizer that I feed to the rhododendrons. I haven't been able to bring myself to prune the shrubs despite their need of a bit of shaping. I've limiting pruning to what little I cut for Christmas. The growth rate is slow, so slow that cutting much off seems ill advised or more precisely painful for this gardener.
This isn't the first year, Blue Girl has had berries, but she does have more than ever before. Now, there are a few hollies in town that are doing better, but I'm comforting myself with the idea that they are older plants and that the Blue couple in my garden will be more fruitful as they mature.