Star Guardians and Dark Stars related?

So, if anyone from Riot can, explain to me this one thing.

Do the Star Guardian skins and the Dark Star skins have any kind of connection with each other? Some friends and I were discussing this after seeing a lovely piece of artwork by suqling with SG Janna and DS Thresh (this one in case you were wondering https://66.media.tumblr.com/2a9130795e24981c588edf3bb34cc8c3/tumblr_oekux8xOy11r6o1dao1_1280.png )

Thresh looked like he was straight up pissed at Janna for what seemed like "leaving them to die". Whatever happened looked like it had completely corrupted Thresh and caused him to become a Dark Star, but then some how got Varus involved (possibly through brainwashing or manipulating him to turn against the Star Guardians).

So if that's the case, were Thresh and Varus part of the original Star Guardians mentioned in Janna's SG bio? Is their corruption the reason why she's never talked about her original group? Did Thresh make Varus turn against the original SG group or did he himself betray them causing him to become corrupted? Are we going to get to know/see who the original Star Guardians that again were mentioned in Janna's bio and what exactly happened to them?

Another point I'd like to make out is this: In SG Jinx's voice lines, she doesn't even seem to care about her role as a SG and just... Doesn't seem to care about the rest of the team either except for Lux. A couple voice lines from Jinx sounded like she has some amount of respect towards Lux despite saying she's "boring". So my question towards Jinx is this: Is there a possibility she herself could become a Dark Star given the time?

Thank you! —Smyertch