Try naming them. Not the category, the actual names, in the order of who you would ring at three in the morning without rehearsing the first sentence.
The list is usually shorter than people expect, and that isn't a poverty. Four is a lot. Two is a lot. Most of the loneliness in the world sits somewhere below one.
Gratitude goes vague when it stays plural. It sharpens the moment a name is attached, and with the name a specific thing that person did. The fortnight they phoned every evening. The meal left on a doorstep. The message that arrived on the right day without being asked for.