I believe each child is very unique as you have mentioned, you can take those pointers as a reference since a girl and a boy is very different; moreover even between siblings their behaviour can be very different.
Especially middle child syndrome.
I agree it is not easy to love your kids all equally when you have more than one. I see my brother struggle at times to be as fair as possible.
That's part and parcel of life.
upvoted
RE: 11th Parenting –Observing a Child: Socio-emotional Development