OoP : Sirius BIG question no-one has asked before (spoiler)

[Sayuri]

No: HPFGUIDX 65994

--- In HPforGrownups at yahoogroups.com, "sueeeyqbong" <sue at s...> wrote:
> The phrase 'cousins by marriage' can refer either to 'Molly 
married 
> someone who was my cousin' or 'I (ie Sirius) married someone who 
was 
> Molly's cousin.' I don't think the former can be the case, since, 
if 
> it were, Arthur wouldn't be Sirius' second cousin once removed, 
but 
> his first cousin by marriage. 
> 

"Cousins by marriage" in my family always meant someone who was your 
cousin through marraiges but not a blood relative. For example, my 
Aunt (not a blood relative, the woman married to my mother's brother)
has a neice. She is therefore my cousin through marriage, but not 
my "actual" cousin. If this is a similar definition that Rowling is 
using, there is no reason at all that both Arthur and Molly could be 
Sirius's cousins.

On another note, even if Molly IS Sirius's blood-related cousin, why 
couldn't Arthur be his cousin, too? It seems to me that the Black 
family tree is a major indicant that the pure-blood wizarding world 
is horribly inbred, much like the European royal families. A 
marriage of distant cousins (Arthur and Molly) wouldn't be out of 
place, then.