Dragon Attack: Blood of the Dragon only gives its attached character the dragon trait while participating in a challenge, so you could not kneel the character with this card as it would already have had to kneel to be eligible, if you see what I mean.
There are ways around that, like Distinct Mastery or Mercenary Contract.
Balerion the Black: Similarly, this card would force Blood of the Dragon to kneel as it could only avoid the effect if it had already kneeled.
That is correct 99.9% of the time. It is, however, actually possible to engineer a situation where Blood of the Dragon would protect from Balerion, using Shadow Politics.