Anyone else's LO not laughing yet?

Amy • Married 4/4/2012. Baby #1 born 3/18/17 💙! Boy/girl twins due 2/18/20!

My little guy is 17 weeks old today and isn't laughing yet. He smiles hugely and does a cute gurgle like he's maybe going to let out a laugh, but not quite there yet. Is this abnormal??