You never know who you're going to meet when you sit at a table to roll with a new group. And you can meet ANYONE in a new group. If it works out, you'll have a group of friends. If you're lucky, you end up with a new best friend you can go to and lean on when you need. Like my sis <3 If you're really insanely lucky, you may even meet someone more special than the others. The person who makes you laugh and smile more than anyone else, makes you feel like you're special. You may find someone to love. If someone had told me when I went to sit down with the DM and work on my first character that, six years later, we'd be married (and it's about time you two got married!), I wouldn't have believed them. We were really lucky.
There's a lot of varying opinion on two people around the table being a couple. Most people won't care (Example: our group). If this is your group, congratulations. You've got a good team at your back for when trouble rears its ugly head. Or heads, in most cases. With others, though, it may cause some concern, and it's within reason (I have several good stories for this). If the couple is two players, there's concern of them doing special things for or favoring each other over the other teammates. If there's a break-up, what happens to the characters in question? Some DMs might not even play with couples to avoid potential drama. There's also the risk of distracting each other while playing, or having a lovers quarrel over the table (With every group I've been in but ours: EVERY FLIPPING TIME). If it's the DM and a player, other players may be concerned about favoritism, and what's going to happen if the player's character accidentally ends up the victim of a failed save? For people not in a relationship with another player, there's a lot that feels like it could go wrong. Heck, for those IN a relationship, there's a lot that feels like it could go wrong, especially when the relationship is newer.
I didn't know how dating my DM was going to work out. I wondered about most of the above when our relationship was new (although I didn't have to worry about how our other players felt; they're the ones who got us into it in the first place!) It worked, though, and I believe most of it was because of one simple idea: When we sat around the table, we left everything behind. We still loved each other, and still do, but when we sit at the table to play, it doesn't matter. Bring dice to the table. Bring papers, pens, computers, books. Don't bring your relationship, and DEFINITELY don't bring your drama. The in-character drama is so much juicier anyway.