RE: It’s Not My Baby, But My Wallet Thinks Otherwise: I May Not Have Much, But I Give What I Can.

Children grow very quickly, you should always buy sizes larger than their age. I recommend buying sizes from 12 to 18 months so they don't lose them so quickly.
Continue your work as an aunt until you feel ready to have children of your own. The clothes are very pretty. I hope they fit your nephew very well and he looks handsome.