I'm just 31 myself, but sometime I feel so much older. I have three younger cousins (all girls), who are married with kids. Some time ago, I was talking to yet another relative, and actually used the phrase, "when I was your age"; I immediately thought, "this ain't supposed to be happening..."
Its hard for me to believe I'm already out of my 20s; I still feel so much like a kid. Movies, music, and games were my world for years, but I'm now starting to feel "empty" on the relational front. My mother, sister, and grandmother are great (most of the time); I just feel stuck at some kind of impasse.