So that’s a lot of words :) Can you help me narrow down to a set phrase / a few words? Thanks for taking time to read through my question :P
casual speech, you might try something like "build on each other":
"Curiosity and knowledge build on each other. The more you know, the
more curious you will become, and vice versa."
"Cause each other" might work: "Poverty and corruption cause each other. When one increases, so does the other."
In some cases, you might be able to anthropomorphize with "scratch each other's backs": "Education and healthcare scratch each other's backs: as a population becomes more educated, it usually becomes healthier, and healthier populations are better able to learn."
Some related concepts in formal speech:
"If and only if" means that two things imply each other, rather than cause each other.
"If a cat is in my house, it must be my cat. Since I never let my cat go outside, my cat must be in my house. That cat is my cat if and only if it is in my house."; "The Saudi economy and the oil market are closely linked. The Saudi economy will prosper if and only if the price of oil remains high." In math, logic, and computer science, "if and only if" is often abbreviated as "iff".
A "vicious cycle" or (less commonly) a "virtuous cycle" might be closer to what you want.
"The McClintoc family killed my father, so I killed one of their sons in revenge. Then they killed my mother as revenge for me killing their son. It's a vicious cycle."
"Positive feedback loops" are also in the same group: an effect amplifies its own cause.
"When the globe warms, ice melts, revealing land and water. Ice reflects most of the light that hits it, while land and water absorb light, which creates heat, accelerating global warming, which causes even more ice to melt. Positive feedback loops like this make global warming an even more intractable problem."
"are correlated" shows that things are linked without making any assumptions about causation: "Life expectancy and happiness are correlated."
Lets say A = "It's raining" and B = "You are using an umbrella". In this case we can probably say that A <=> B. (Let's pretend you live somewhere where it usually doesn't snow - or let's call snowing raining as well.. In some sense it is that.)
Not sure how you can use this in everyday speech, but maybe it gives you an idea.
For tidiness, I'll copy my answer to the question thread here. And one more option: "interdependent" or perhaps "inextricably linked."