Well, allow me to explain a bit more.
I have two champions. They are separate (However if people prefer I can definitely change lore and add a few things to make them into one champion).
They would be two separate in the store, and they would be completely functional WITHOUT the other one on the team.
I'll give you an example. The guy has two Passives. One of the passives only takes effect if the girl is within 1000 units of him. This passive gives him a bonus to his attack damage and attack speed as well as a shield for her. The shield of course can be destroyed and takes time to be renewed.
The other passive he has gives him stacks that enhance him, but are lost upon death.
The girl also has a passive that gives her bonus to her ability power and attack speed. She also has a passive that works without him. This passive gives her bonuses to her stats which (Just like his) are lost upon death.
They each have a passive as well that does nothing on its own but works off each other. She has "Symbiosis" which infect targets after 5 stacks have been accrued by her and on all abilities that hit enemies. This gives his abilities "Bonuses". An added effect besides the initial effect. He has "Infection". This infects the target when being hit by his abilities, not basic attacks. The infections enhance and give added bonuses to her abilities.
HOWEVER their abilities already work WITHOUT the other one being in battle and within 1000 yards.
So, they work without each other, but with each other within 1000 yards they gain bonuses as well as the addition of their Infected and Symbiosis passives that give added bonuses to their regular abilities. However, they do not need this to function.
Hope that cleared it up. They are regular champions, but together gain bonuses off of one another so they don't HAVE to be together but there is a definite benefit to being together. I just wasn't sure if this would make a good addition to league because people may think it might be too OP and it would be stupid for people not to pair them, but to me people don't HAVE to pair them. I wanted people opinions on what they think about the idea or if it isn't for league or would make the whole meta broke and league just a whole "Gotta use these two or you're screwed" thing.
I myself think they are fine, but might be seen as OP. Let me know ^_^