In lore, there is only one battle at the end of the Death Knight starting area. All Death Knights were there at the same time in lore. We roleplay it out differently, and in actuality, we see it at different times, but we were all ‘there’. All player Death Knights worked together at the same time.
Does this mean that we’re all supposed to know each other? A lot of people don’t like this idea – it’s a little like saying that all the draenei ought to know each other, because they all came down on the same ship, and this also seems to be a little flawed. Well, that’s certainly true, there is a comparison to be made there, but let’s be honest; whatever the actual stats on play say, there are a lot more draenei than there are Death Knights.
But how well should the Death Knights (and indeed, the draenei – let’s expand this out a little more) know each other? There was reportedly only a ‘small legion’ of Death Knights, but this is still a pretty high number. I can tell you, after three years of classes with the same maybe 100 or so people, I couldn’t tell you anything about the personal life of even a fifth of them. I could barely give you a list of a quarter of the names. If someone gave me a list of 200 names, I might be able to pick a fair percentage of them as being from my classes. Maybe.
As Death Knights working together for the Lich King, or as draenei on a big ship together, how much could we expect them to know one another – more or less than my example with the hundred students I have classes with? There were more than a hundred Death Knights, and way, way more than a hundred draenei. There’s also no reason to believe that any given Death Knight or any given draenei would have had any contact with any given other DK/draenei – after all, the Lich King’s services spread far and wide, and the draenei ship was a big place.
So where does that leave you for roleplay? Well, if it really concerns you, or interests you, and you really want some kind of connection to someone else, drop them a line out-of-character and ask what their feelings on it are. This works in other situations than just the draenei and the Death Knights, of course – if you’re both human priests, maybe you were in training at the same time and the same place, for instance. If you want to have a connection to someone else, which can be a lot of fun, there’s no harm in bringing it up to them.
(In a polite way, of course – it might be weird to message people and ask for particularly intimate or gory connections, but to suggestion some kind of shared backstory normally wouldn’t be out of line.)
Otherwise, if you don’t want to bother them, or something they’ve said really makes you think that they would have at least some kind of connection, there’s no danger in playing it low-key. Maybe you recognise them a bit, or have a fuzzy recollection of them, but not a strong one. Or, of course, if you think there’s some chance they may have met before in their backstory, bring it up in character. “You were born in Tyr’s Hand? What a coincidence – so was I!”.
A lot can come from this – even if they didn’t really know each other before, they may be able to bond over shared experiences in the present. You never know unless you try to bring it up somehow, so don’t be afraid to communicate about the matter.