Brother From Another Mother

Lyrics: Unknown
Music: Unknown

Played by Vince Welnick with Gent Treadly on 20 August 2003. I've no idea where the song comes from, and the only lyrics I can make out are:

Brother from another mother
Brother from another mother
Brother from another mother
Brother from another mother

and:

Sister from another mister
Sister from another mister
Sister from another mister
Sister from another mister

The title in the setlist is "Lover For Another Month", which must be a mis-hearing.