に
ふた
None
The kanji two and the radical two are the exact same things. Therefore, you know the kanji for two already!
Think of all the things you have Two of. What is the most important? Some would say eyes, some would say ears. I would say the knee (に) because if you didn't have them, it'd be really hard to go up stairs.
Currently there are no similar looking kanji which exist in the WaniKani learning system