I, on the other hand, find that ironically the loli characters are the best partners/companions for N°6.
Lilith can be a mad scientist, but she knows better than to push N°6 too far, and care for him in her own, twisted way (she build Alice as his partner, after all).
Rose is too pure and respect N°6 a lot, even if she is aware that he acts like an idiot most of the time.
And Alice is just the perfect partner for him, hands down. She is the one that understand him the most and is always trying to help him, one way or another.
Too bad N°6 like them big haha.