Is it normal to secretly record peoples' conversations?

It's illegal to record people's conversations without telling them Bit lots of us do. I'd like to be a fly on the wall heaps of times and see what people say about me.
Parents? OF course they talk about you. That's what parents do.

People are gossipy by nature. Don't worry about it. Even the coolest people get shit talked behind their back.

Just don't get butt-hurt if you hear things that piss you off. It's the risk you take for sticking your big nose in private discussions

Have you never heard the very old saying that eavesdroppers never hear any good about themselves?

Apart from the danger of hearing things you won't like, it's disrespectful and probably illegal to record people without their permission: how would you like it if your parents did the same to you?

It is probably just going to hurt you. Parents talk shit about their kids all the time.

If it's your parents, I say screw it yeah, record away.
Although be prepared for something you may not want to hear. My friend did this once to some people - similar situation to yours - and what they said was very harsh for him to hear. But also, it allowed him to deal with things...so it's a double-edged sword.
Generally bad, but for your parents I say do it.