There is a difference between siblings and usually it’s their personalities. My firstborn and second born have different personalities and it can be seen. I tried playing with my firstborn when she was just 3 months and not a hint of a smile out of her. Despite smiling widely till my face felt that it was about to split into two. My second born is naturally playful. She broke into a wide mouth grin whenever she sees me smiling at her. Just seeing her grin makes me happy.
The second born loves to play and it is just so fun playing with her and forget about the troubles. I hope her cheerful disposition stays with her and help her tide over challenging times. She is also more prone to distractions and want to check everything out. Not a bad trait but it does create another set of problem for me, I need more eyes on her. The firstborn was terrified of any loud noises. Yes, she ate a lot of that bottled powder that the elders recommended.
With my kids still so young, I can see the differences between them. One is more introverted, the other just feels more extroverted at this moment. Not that the younger girl will smile at everybody she sees. She smiles only if she feels familiar and only at guys. I wonder, what is the deal with guys? The second born tends to be vocal about her happiness, by screaming. The firstborn was just about laughter but never ear pitching levels.
Between me and my siblings, we do have different personalities too. As they did say, everyone is an individual and children, are individuals.