Each of us was born into this world through a randomized process that was not created by humankind: the genes you were born with, the environment you were given before you could manage your own affairs, the accumulation of genetic mutations over the course of countless millennia that resulted in who you are today. This is the opportunity you were born with.
To think that we can compensate for this random process with any level of precision is to wage war with nature, and I'd bet that nature will win.
It is an admirable goal, and certainly we can take steps to reduce inequality of opportunity. But true equality of opportunity, or anything close to it, is unattainable in this universe.