Billdo and Green Bean are brother and sister.
Here is a relatively recent thread listing couples who met on the SDMB.
Dan Turk is my brother. And he’s a little shy with the capital letters.
JustPlainBryan and I are spouses. Papaveraceae is my loooover-girl.
No, not really, but she is a very good friend of mine. 
Suburban Plankton and I are married (11 years last month!!)
Kal and I are married - 4 years in August 
I’m related to Ninevah
I have been wondering if there’s any chance that Jenny Haniver and I could be related (assuming it’s her real name). Hanniver was my Grandmother’s maiden name and it seems to be very uncommon.
stormchaser and I are married.
My step daughter occassionally reads the boards but has not joined.
I’d pony up the $14.95 if she’d ask
Parallax is my hubby. Our kids are too young to read. I don’t know if any other relatives read the boards.
There’s this SPOOFE asshole running around the boards that I’m somehow related to, if I’m to understand correctly.
AnitaVacation is my sister-in-law. Harald Bluetooth is my brother-in-law, as is jimbobboy.
Cyn is my aunt. She’s the one that told me about this place.
Closest I get is to iampunha - we’re distant cousins. Other than that, nada.
But hey, it qualifies!
Mama Tiger is my mom. I try not to let it affect my posting in the TMI sex threads too much, but ack! My mom might be reading it! We’re both unable to resist reading a TMI thread…
My brother registered here once at some point, but I think he only posted once, and I don’t remember the name he posted under.
So the current crop of Doper couples is, to my knowledge:
Married
Anniz and Montfort
Auntie Em and SkipMagic
Brynda and RickQ
Elenfair and lno
Geobabe and UncleBill
GingeroftheNorth and Weirddave
Heloise and Coldfire
laserkitty and thinksnow
Miss Creant and MrCynical
MsRobyn and AirmanDoors
psycat90 and Demo
Shayna and Spiny Norman
sperfur and withaK
True Pisces and Verrain
Engaged
fizzlestothetop and iampunha
Honeydew and Emofkuniv
racinchikki and gunslinger
vix and SuaSponte
Zyada and rjk
bodypoet and todd33rpm
Drachillix and Cyn
Nocturne and UnwrittenNocturne
:: nudge ::
sniff
Parallax and I got left off the spouse list too…
Sometimes I claim Sauron as my other half.
I am married to leenmi.
Twickster is my ex-wife.
I kid. I kid because I love.