I don't think so if you don't count Fang and Vanille, but I haven't double checked
Ashe and Vaan
Ashe and Balthier
Ashe and Basch
Ashe and Fran
Ashe and Penelo
Balthier and Fran
Balthier and Penelo
Balthier and Basch
Balthier and Vaan
Fran and Basch
Fran and Vaan
Fran and Penelo
Basch and Penelo
Basch and Vaan
Vaan and Penelo
I'd say Fang and Vanille are a grey area. On the one hand it could be argued that they are romantically involved. There's definite possibility for that in the subtext. But, on the other it can be argued that their bond is more sisterly than romantic.
I was thinking more about confirmed non-heterosexual couples. Of which I don't think there are any.
Larsa x Penelo is the only right choice.
There's also a very devoted slash community to older guy and younger guy though. I've seen a lot of Gabranth/Larsa and Snow/Hope.