On page 16 of the rules, it states that stealth is declared against the original target in case of a title Supporter jumping in to help. I assume this is occuring in the Player Action Window just after the attacking player declares stealth and the defender is supposed to kneel defenders, the latter action not occuring hence the Supporter jumps in to defend instead.
Is the exact same principle applicable to redirects with the Crown Regent and the Lord Commander of the Kingsguard? The rules don't explicitly state it but I am guessing its the same?