Try pulling your subjects further away from the background, that will help you avoid harsh shadows behind them. Gr82cre8 is right about checking your lighting (mwah, Gr82cre8!), but you really only want to have only one source of light. Window light is the best, as ceiling lights will give you shadows under the eyes.
I think it's easier to take photos outside, in the late afternoon when the sun is low in the sky and puts beautiful light in the eyes. Here's a nice article
about taking holiday pics.