EDIT: I didn't see Joshua's post before posting this.
The question is an excellent one and I am still thinking about what to write further.
As we see in other discussions that focus on translations, there is considerable peril in looking solely to dictionaries and taking definitions out of context. Especially in the case of Epicurus, he uses words in non-standard ways when he believes that the popular opinion of it is inaccurate (example - "gods"). So you have to really be aware of the sweep of the remaining texts to make sure you don't take something out of context that contradicts the whole.
I would think the best way to proceed would be to first look at what we know of the actual lives of Epicureans and how they lived in the ancient world. And even after we do that, clearly there are lots of shades of intensity of friendship so that those so that those at one of the spectrum are hardly recognizable as being in the same category as the other end.
That's what you are illustrating in this question:
Are there bounds to the concept of friendship in the sense thought of by Epicurus (the characteristics of it and the specific benefits it provides) that rule out other forms of kinship with human beings, kinds that do not even necessarily require knowing the other person?
Surely the answer to that is "yes there are bounds" at least in the sense that there are differences in the way we deal with them. It was the Stoics that asserted that there is a divine order of things whereby all humans are bound together in divinely-ordered ways. Whatever else we might say about it, the Epicurean view seems to have been much more practical than that, and would turn on the specific people, places, times, and cirumstances, just as does "justice" (as explained in the PDs).