What squad members romance together without Shepard?

No, this is one of only two visible romances on board, other than your own. The other is Ken and Gabby, as per @ERazER's comment. I personally haven't seen that one. While it may be implied that other relationships may happen, there isn't a scene to walk in on for them. In any case, they don't involve your squad mates, except Joker and EDI. Can't see them making out either.

Ashley and James Vega hook up during the Citadel DLC: