My Stepbrother secret-possession

Leigh is the last person I should fall in love with. He's my earth forbidden fruit.
Who I happen to desperately and utterly need just like human need water and air to survive. He's my ultimate sin. Surely, I'm definitely going to hell for him.

If love Is a sudden feeling of combine emotions, an unbearable physical attraction and an intoxicating rush of feel-good chemicals, a certain desire to care, respect and prioritize another's well-being, developed between two people and thrive over time. If it is what we need to survive just like we need air to breath. Why is it sadly limited? Why is it confining and torturing.