Loving-Kindness

So I have tried the loving-kindness exercise a few more times since I first blogged about it and am having a little more success taking in the suffering of others. I find this much easier to do towards those who are close to me (fiance, dogs, mom and the like) but very difficult to do towards strangers. While trying to do so, images of people I know pop rather than the unknown because they are familiar. When this happens I try to avert my attention to the people I don't know. Does any one else run into this habit?