Orphans are proof that we haven't evolved nearly as far as we believe. The need to procreate and project our bloodline into the future, no matter how flawed, is buried somewhere in our DNA, probably along with other useless and corrupted things that shouldn't define us. If it had an actual purpose for our survival, that purpose was made moot by forming societies and civilizations.

Animals adopt orphans all the time without concern for bloodline. They often even adopt across species lines. Humans are so infatuated with themselves that they can't be bothered with their fellow humans unless they are a "mini-me" copy of themselves.