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

[sueeeyqbong]

No: HPFGUIDX 64539

Yet another possible future plot which sruck me whilst reading 
the 'Sirius and Harry in front of the Black family tapestry' scene 

Sirius says (UK version, page 105) :

'Molly and I are cousins by marriage and Arthur's something like my 
second cousin once removed.'

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. 


So...is the latter the case? Was Sirius married once?

Can anyone else think of any other interpretation for this sentence? 
If you can, I'd love to know. I'm only just coming to terms with the 
tragic circumstances of the last year of Sirius' life - if it turns 
out that he was once married and yet another tragedy meant that, by 
the time he met Harry he no longer was, I think I'll be done in. 
I'll have to take a month off work to recover!   ;-)

Sueeeyqbong