Eh? No, it happened long ago, I don't mind. [ he does mind. Not about his father, but his mother. Kaneki never got over his mother passing away, no matter what he tells others and himself. ]

Uhm- I don't want to bring up such depressing topics with other people. It's not really fair to bring them up like that. [ most wouldn't even know what to say. And that's fine, really, Kaneki doesn't want to put this sort of burden on other people because he knows it can be awkward and sad. ] It's not that I don't trust you, it's just- [ he was taught not to burden others. be kind. be gentle. ]

I don't want to make the conversations awkward. [ kaneki wants to make the people he cares about happy. And he doesn't want them to feel like talking to him is depressing ]

... I'm extremely gloomy. [ he smiles, a little apologetic ]