Its the mother’s fault 100%.
Don’t lie about something as life-changeling important as the paternity of a child and these things won’t happen.
A man’s life is fukked up because he put five years into financially and emotionally rearing and raising a child that he thought was going to carry on his legacy that turned out to have no relation whatsoever to him.
A child’s life is SHATTERED because his sense of identity has been based upon a lie. The bond he formed with the man whom he thought was his is severed. And there is no guarantee that he’ll have the opportunity to know his true father.
I hope the mother is able to reconcile the consequences her heinous actions have reaped upon her child and that she takes responsibility and does her best to make it up to her son.