Daniel Cawood (Catherine's son) - what if?

It was Daniel, who raped his sister Becky, and Ryan is Daniel's son? I believe it's more likely that Becky would commit suicide, if she was raped by her own brother, than if she was raped by a none family member.
And maybe Becky didn't commit suicide at all, maybe she was murdered - by Daniel, so she wouldn't tell - and it was made to look like a suicide.

It was the very last scene in season 2, when they were walking up the hill, and Catherine got this horrid look upon her face, that made me wonder.
Most people say she was thinking about Ryan - and his future. And yes it could be that, but I got the feeling throughout the show, that she was always thinking about that.
She often seemed angry at him, said horrible stuff about him, and she told Daniel, that she wished he died and not Becky.
If Catherine is capable of these thoughts, I would argue that it would have crossed her mind many times before, whether Ryan would turn out like his dad, and therefore it was something completely else she was thinking.

It was Catherine's look on the hill, Daniel is suddenly kicked out by his pregnant wife. "She has these weird ideas!" What ideas?!
And the fight Daniel had with his parents in season 1. I got the feeling, that Daniel wasn't only angry with his parents, but with Becky too. Like he hated her, perhaps a love/hate relationsship that made him rape her.

What do you think, is it possible?