It's certainly okay to use real examples that you know, but if you can't think up examples of people you don't know, then you're not opening up the Compassion/Lovingkindness meditation enough. We want to open up our vision to everyone in the world. We want to think of all types of people, everywhere. We want to think of all ages, all occupations, all races, all religions, all types of people, in any state or form, injured people; people without legs, people with legs, and so on. We want to open it up, open it up, open it up. When you open it up, then the D/D method is not going to be difficult, whether you know people, or whether you don't know people.
What's it like to think of being a 95-year-old person who sits all day at home, hoping the children, the grandchildren, or the great grandkids would please come to visit? What's it like? Can you identify with when you want someone to come see you? Think of someone 95 - it's all day! Days and days go by for a lot of those people and nobody comes to visit.
I visit my mother in a retirement center. There are 2,000 old people in this center. It's a huge place, like a little university campus, with a swimming pool and all sorts of things. Some of those people never have anyone come to visit them. Their sons or daughters don't come. One woman that we knew quite well, her son who only lives across town, would rarely ever come. What's it like to be lonely in this way? If you can identify it in yourself, then multiply that Dukkha for someone who's 95.
Every different degree of whatever you can imagine while sitting on the pillow, open up the Compassion/Lovingkindness meditation, get it to every single degree you can, to every type of Dukkha you can, every age, and so on.