Getting one to talk about his day at school feels about as painful as pulling teeth might be. The other one makes my ears fall off while recounting the most minute details of her doings.
One hates organised sports of any sort, though he will happily hike a 7-km trail. The other one practically begged me to sign her up for badminton and karate classes.
One practically inhales books and is to be found with his nose in one even when he should be concentrating on other vital activities, like walking... The other one loves screens and, since she is mostly deprived of them, is even happy to stare at Excel sheets that I might be working on.
One is a complete foodie who loves to eat, cook and read about food. The other eats to live and would be fussy if I let her. (On a solo visit to her grandmother's place, she had managed to convince her that she did not eat red food of any sort!)
Seriously, nothing kills your delusions of control over your children's personality more effectively than having two or more of them...