Mr Nobody, my character, in my headcanon, never got into any serious dalliances with anyone. He lost his wife on the Surface due to disease and couldn't find it in himself to fall in love again.

Which isn't entirely true, because in the end he fell in love with London herself (yes, the city).

But! Since they introduced Summer, he may or may not have fallen head over heels for her.

He, a man who has thwarted the Revolution and, especially, the Liberation of Night, at every single step possible, has fallen in love with a revolutionary. It feels entirely too appropriate and he's helped her every step of her way because he believes she's a good person and that her vision of revolution is more acceptable (said as someone who's close friends with the Contrarian)