There are many fanfics written about Fred and George, and some of the threesomes are hard for me to accept (ahem, personal opinion). Everyone sees twins as the same individual, but in my eyes they are different. Everyone is different. They are not the same person, so naturally everything will be different. Twins are not necessarily the same in everything, including how they treat others, their outlook, and so on. In the original book, Angelina was Fred's dance partner, but in the end she married George. I prefer to see it as the two of them comforting each other and licking the wounds of the deceased, because in that case, maybe only they can understand each other's pain better. (The above is my personal opinion, please don't comment if you don't like it.)
Purpose: Don't ignore individual feelings