We first hear about him when he suddenly shows up at Rip Hunters' lab (*1) claiming he's a Blue Beetle from the 27th century that can save Ted Kord. Mr. Mind calls him "Joshua" which we later learn is similar to the name of one of the scarabs in Jaime Reyes first series. He also claims he's trying to save a female when he confronts Ted at the end of the Blue and Gold arc.(*2) All of these are lies he told and he later smugly tells Booster he'll use whatever story he wants to misdirect people. Which is probably one of the only honest things he ever tells anyone.
Before Max Lord returns Black Beetle seems like he'd be the likely candidate for Booster Golds' archenemy since Mr. Mind will always be considered more of a Shazam villain. Yet throughout the series he never seems to fit the role. Booster doesn't have that much screen time with him once his true colors are shown. As far as we know there's no personal history and Jurgens doesn't seem to think his appearances in Jaimes' Blue Beetle series (*3) fits the direction he had in mind.
The person Black Beetle suits best as a foil is Rip Hunter. Who's identity is hard to piece together? Who knows how the butterfly effect works? Who's a mastermind with plotting? The answer to all these questions is Black Beetle and Rip Hunter.
In fact the Day of Death arc marks the only time a villain has really succeeded during Jurgens run. Black Beetle destroyed the Titans in the past to create an alternate timeline just to get a red scarab that wouldn't otherwise exist. It doesn't matter that the Time Masters would later undo his work because he got what he wanted. When he's stating this it's not to Booster but Rip. During this arc we get what many BG fans felt was a telling piece of art with two panels side by side. Rip and Black Beetle in similar poses. While Jurgens could be hinting at an alternate/evil twin Rip since he doesn't shy away from doing plots with doubles there could be more to it. I want there to be another explanation because the Rip answer is pretty anti-climatic. At least for me.
It also lacks sense because Black Beetle would be aware of Rips' identity if he was a different version or a twin. Maybe not if he was a regular sibling that didn't know his background but an identical twin would at least have some idea they were connected. An AU Rip or identical twin could and would easily exploit the situation to his benefit. He could replace Rip to make Booster do his dirty work or use Rips' image to trick others into giving him what he wants. While it could be possible it seems like the only people mad at Rip are "Rex Hunter" (who broke the rules), sometimes Booster when they disagree and the Linear Men (who likewise broke Rips' rules.)
Black Beetle is the master of misdirection so it would be kind of weird if the answer were that easy as well as it raising all sorts of questions. There's also a lot of other factors to consider. His story was linked to Teds' and his image has been noted by many to reflect the style of Kingdom Come Blue Beetle. Why did he jump into the time sphere along with Ted? He might have been lying about trying to save a woman he knows but there had to be a reason for his actions. Ted shouldn't have been a match for his power yet Ted still went back and died despite Black Beetle being there? Doesn't it seem a little careless and convenient that his scarab apparently falls off during this? If it's the same type of scarab as Jaime wouldn't he be naked without it? What did he gain?
Some time after the two beetles in a pod bit Booster loses the scarab and we see a figure with it saying "open sesame" near the end of the Johns/Katz run. This is important because the mysterious person laughing is supposed to either be Ted or Black Beetle. Later on in the series Booster uses the phrase as a joke when he comes into the room (*4) stating it's a hidden lab Ted put together that only they can enter. It's locked with Booster and Teds' DNA to prevent anyone else from entering. Open and shut case that means the person has to be Booster or Ted, right? Well maybe not. There are two other important times DNA comes up in the series. The first is the Supernova suit which is keyed to Boosters' DNA but anyone in his family can use it. Which means it might be possible that Teds' lock works in a similar manner. The next time comes up with Black Beetle himself as Skeets tries to scan his DNA. He doesn't get a complete scan but won't tell Rip anything. In fact he seems almost suspicious of Rips' intentions.
Jurgens has teased that Rip might have fiddled with Skeets programming but if he did it's obvious he didn't make Skeets blindingly loyal to him. I don't think Skeets mistrust has to do with a DNA match with Rip because: a.) he'd just tell Booster he doesn't trust Rip because of this or b.) he'd assume it was an alternate reality Rip. We don't see Skeets really question Rip like this anywhere else under Jurgens. If he did scan Rip it would also mean Skeets would know Rip was related to Booster and my theory is Rip programmed him not to scan his DNA. Otherwise Skeets would be more trusting of Boosters' kid. So why make a big deal? Well what did Skeets and Rip disagree about that affected Booster? Ted Kord.
Skeets was more understanding of Boosters' desire to save his best friend than Rip was. Boosters' refusal to stop trying led to a pretty brutal lesson to boot. When Skeets scans Black Beetle he say "impossible" which seems odd if the Rip theory were true because he'd know it wasn't given time travel and the mulitverse. He still obeys Rip's order to flee and the most important fact that he doesn't have a complete scan. Just enough to information that's familiar and surprises him because the person he assumes can't be Black Beetle seems to be one he scanned.
There seems to be some connection there and while the comparison to Rip might be a red herring it seems to imply their equals. Much like Blue and Gold. One of my favorite scenes in the second series has Black Beetle stalking Rip at Vanishing Point pondering who he really is. Really a lot of what he says can be applied to himself. He asks why Rip chose his name well why did he chose to model himself after the Blue Beetle image? My theory which is likely wrong is that Black Beetle is related to Ted. I'd like to say his son although I don't think he's had any love interests since his solo series. Ted did have an evil intelligent uncle though so maybe a cousin. Still I find the idea that Blue and Gold have sons that are rivals very compelling.
It would explain how he could get into Teds' lab and his interest in Blue Beetle. Skeets thinking his partial DNA scan being impossible because he thinks it's Ted when it's a relative. We don't know what happened on the time sphere but it should also be noted that they were in a Time Stealer sphere. You know, the ones that are ridiculously hard to operate since it's a cruder copycat version of Rips' invention. We don't even know if Ted could work a normal one much less a vehicle that Booster--an experienced time traveler--had trouble using due to the clumsy design. Black Beetle however knows how to use it.
If Black Beetle were Teds' son it'd not only create dramatic tension it also has Blue and Golds' kids in some what reverse roles from their fathers. Rip being the inventor and as far as we know Black Beetle being the thief. Rip is known for being a excellent hand to hand fighter while Black Beetle uses power sources he stole. Rip follows a legacy based on good intentions while Black Beetle seems more selfish. There's a lot of potential with this concept.
*1 This isn't actually that impressive since Rip doesn't exactly hide where he's at and TMVP shows he's not the only Time Stealer to do this.
*2 While Black Beetle is known for lying I'm not sure why he would bother lying to Ted about a loved one. He has to know one life isn't going to sway Ted after he saw countless people dying in the Omac world.
*3 Which means that he's not Hector or Jaime.
*4 Jaime is with Booster and he as to give him permission to enter the lab. DNA is key to this plot.