Huh? He only has one kid- a son, who appears in a lot of the movie diving with him. I'm no expert on the filmmaker's life, but I've not heard that he 'turned his back' on his wife. In fact, you can read her feelings about his relationship with the octopus here:
She ends by saying that she dives almost every day with the filmmaker.
That does make me feel a bit better about it tbh. My main takeaway from my first watch through was "what are you doing obsessing over an octopus while you have a family at home that you seem to have forgotten about."
I almost stopped watching it during the first few minutes for the same reason, you just have to get past that first bit and get to the first underwater shots.
It's an incredible film, definitely my favorite nature film.
It might be useful to learn that the narrator was depressed and documenting the octopus helped him heal.