system
nostalgic: I am feeling this way because my son is having a birthday soon. I can't help but think about when he was smaller.
gpt
My son is turning two in a few months and I can't help but think about when he was born. 
gpt
Any big plans? My son just turned 4. I've been nostalgic also.
gpt
Just a small birthday party with family and friends.
gpt
That sounds fun! have you been looking at the old baby pictures?