R1 is right. He's been with Katrina Greenwood for decades. She's a visual artist. They live in inner Sydney, and he seems to be very much domiciled in Sydney except when actually filming.
I notice his Wikipedia page focuses almost entirely on film and TV, but the vast bulk of his work has been on the Sydney stage. He still does something on stage most years: he's about to open in Godot and next year is playing Macbeth.
The son, Harry, just graduated from NIDA: he has taken his mother's surname as his stage name. They also have a daughter.
I've never heard any rumours about either Hugo's sexuality or his behaviour. He's greatly respected, apparently as a person as well as an actor.
I saw him in Uncle Vanya with Cate Blanchett. He was great, better than Cate, in fact.