Simple. It's called the Immaculate Conception.
Well, then Mary did not need to be sinless because what you all claim God did for Mary being born of sinful parents, He could have just as easily done for Jesus being born of a sinful mother.
And Jesus did not have a sin nature because He did not have a human father through whom the sin nature comes.
And He would not be contaminated with sin through simple human contact. That’s not how one acquires a sin nature.
So how far back does the immaculate go, ebby? For Mary to be sinless her Mother had to be, etc. It is your false Christianity religion of Catholicism which claims Mary was sinless so that Jesus would be born sinless, so how many generations back does your false chrsitiantiy claim the sinless brths?