Dumbledore and Malfoy conversation. Is that a clue?

[wapp13]

No: HPFGUIDX 134229

Carodave:
> If Regulus was still alive, I feel sure that Kreacher would know, and 
> consider him (Regulus) to be his true master.  > 
> 


Of course he would know. Dumbledore clearly explained to Harry about 
the order of inheritance of house elves.  No way would Kreacher have 
referred to Sirius as his master if his older brother was still alive 
and absolutely no no no way would he have taken an order from Harry.  I 
really thought that bit was so clear as it was referring to this all 
being tied into magic, not just a 'knowledge' of someone being alive or 
dead.  And we all knwo how greta the magic of house elves is, even 
though they are not allowed to use it.

Wapp13