Well, I know a family with FOUR girls.
They are ALL different from each other.
But, the thing with this family and it being all girls of varying ages is that, they all get along.
It is their parents... and despite all the girls having different personalities... they are all following their own interests and talents. AND they all help... with each other.
The family is very strong that way.
The parents.
They are not the harsh hard core disciplinarian types that wield their 'power' via spanking or black/white parenting. But they teach their kids to look out FOR each other, and that they are all, sisters. Not adversaries.
And the kids, are really well adjusted... nice kids. Really good hearted and not jealous or anything icky like that.
So, sure, don't compare your 2 kids. No matter what gender. And let them be, themselves.
Nurture, 'teamwork' and what being siblings are... and family.
I have sisters. One of them, was REALLY a pain. Major jealousy. She being one up from me in age. She had major resentment, toward me, most of her life. NOT pleasant. And it was also her personality.
So with that in mind, the one thing I can say is: BEFORE your 2nd child is born (and I did this with my own Eldest child who was 3 going on 4 when I had my 2nd child)... is to: PREP your child BEFORE the baby is born. Incorporate her into your pregnancy. So that they 'bond.' Even before baby comes home. I did that with my eldest. I took photos of her each month, with her and my growing belly. She sang and talked to my belly, her little brother. I talked to her about what a baby is: they wake, cry, breastfeed. But it is MOMMY's job. Not hers. That she can tell me ANYTHING she is feeling and I am right there for her. That she is my FIRST baby. Always. I even took her to my Prenatal exams, which my Doc encouraged, and he even showed her how to use the Doppler heart monitor on my belly. ALL of that, helped my Daughter, PREP for her baby brother coming home. She was ALREADY "bonded" with him.... before he was actually born. She thus had no adjustment problems, having a new baby in the house. Being that was she was an 'only child' for 4 years. My kids being 4 years apart.
I treated my pregnancy not as "My" pregnancy... but as a time to acclimate my Daughter, to having a sibling. I used that whole 9 months of being Pregnant... to help my daughter... understand and come to an understanding, of having a new sibling.
all the best,
Susan