I’m Becoming an uncle

Hi All,
I (21M), am a long time reddit lurker, and not a poster, but recently something has changed, I’m about to become an uncle.
My 26M brother and his 26F wife are expecting their first kid.
Whilst I am absolutely stoked for this change, I am also a little nervous for the transition. I am very close with my brother and sister in law, she lived with my family during covid and thus I think of her more as a sister. I’m not sure as to my duties of being an uncle, I want to be there for anything they need but am also not sure of what is crossing a boundary, or is simply something to be kept between them (I’ve been doing my research into childbirth and infants). Simply put, I have no idea as to my expectations or requirements.
Any insight would be much appreciated.
Cheers