This is exactly what is being argued for Blessed Mary and John the Baptist, as well as Christ himself. Do not forget the children and the insane either.
I don't think those with diminished capacity (by age or condition) are exempt from the nature of their birth, but I do think they may not be held accountable for their nature in the same way we are.
Do Catholics believe that John the Baptist was sinless?
Another of those many flexible Catholic positions...
Regards
Yes, from birth, but but not from conception.
Now as the presence of any sin whatever is incompatible with the indwelling of the Holy Ghost in the soul, it follows that at this moment [of Mary's visitation] John was cleansed from the stain of original sin.