I'm going to tell by in-laws about my niece's speech because it seems like they're unaware of it.
Okay, but why were they unaware of your niece's speech? Was it delayed?
I feel responsible. I should talk about it because I take care of her the most.
It's good to be interested in your niece's development. You have to realize parents can be sensitive about others' opinion about their childrearing. However, if you've had a lot of experience raising kids, they should listen to you.
Maybe. I'm still going to talk to them, they're family so they should respect what I say.
It's good that you seem to be caring and respectful towards your niece and her parents. You're being a good family member by doing that and they are lucky to have you in their lives.