Brother-in-law and sister-in-law?

Where is it stated that Caractacus Burke and Elizabeth Burke are the sister-in-law and brother-in-law of Belvina Black? I know she marries a Burke, but Elizabeth and Caractacus could easily be cousins or some other relative. Should the infobox for Belvina state, definitely (as it does now) that Caractacus and Elizabeth are her brother-in-law and sister-in-law? HarryPotterRules1 04:16, May 11, 2012 (UTC)

Yes, this is true. It is not known how Elizabeth and Caractacus are related. There is a theory that Belvina had a father-in-law known to us, Caractacus Burke.--Lord (talk) 12:35, December 22, 2012 (UTC)