Re: walburga/rabastan.
He has been disowned, Rabastan, do recall that. He is no longer my son but that does not mean that I shouldn't get to know his son.
He seems open to the idea at least. At the moment his thoughts, opinions and feelings appear to come from the fact that Sirius abandoned he and his mother with no care or regards given to them whatsoever. Such feelings could easily be used to ones advantage if carefully manipulated and if said feelings are slowly changed and nurtured in a way to make them into something completely different then what they are now.
He could potentially become a public figure if given enough time and encouragement and allowed to reach such a platform on his own...with a bit of help from the right side along the way.