Did someone say "abusive parents"?
However, there is an unexpected parallel between two characters that you might not have compared before: "Papa" from 'Stranger Things' and Sir Reginald Hargreeves from 'The Umbrella Academy'. What makes them similar is how they treat their adopted kids, with both of them dreaming to raise some kind of a superhero team to change the world.
Think about it: Papa would push the laboratory kids to the limit to make them use their supernatural abilities to the fullest, while Sir Reginald Hargreeves wouldn't even bother with his adopted kids' mental health or general well-being.
It's also interesting how both father figures would give their children numbers instead of actual names.
Still, when people give it an extra thought, some argue that even Dr. Brenner ended up being a better father figure for Eleven than Reginald Hargreeves, because the latter didn't even try to pretend that he had empathy towards his children – even though 'The Umbrella Academy' indicates repeatedly that he loved them… in his own unique way.
It makes you wonder what would Eleven (whose powers are pretty similar to those of Viktor Hargreeves, Number Seven of the Umbrella Academy) do if she was raised by Reginald, and not Dr. Brenner. In the end of Volume 1 of 'Stranger Things', Eleven appears to make peace with her father figure despite his abusive tendencies.
For the Umbrella Academy kids, their family drama resulted in an ugly fight during their father's funeral. Now that the siblings have been thrown into an alternate timeline where Reginald is still alive and rules the Sparrow Academy, it seems that their family drama is far from being over.