You mean those that are posted in h-image hosting websites? You may find 2 or more pairs of h-scenes there that are labeled with a single char tag. One of those is the original FK while the others are seasonal variants.Seasonal variants are treated as completely different units and are based from pre-existing FKs. This may not or may also apply to their h-scenes.
Basically, we have
1) Original
2) Seasonal Variants (e.g. Festival, Christmas, New Year, Halloween, Bride, Swimsuit, Shrine Maiden)
Aside from the Original, Seasonal Variants can also bloom so both of them may have bloom (aka 2nd affection) h-scenes. That means 4-pairs of h-scenes already.
Each unit may only have 1-2 scenes max.