@MadMadMadamMim
She will notice. And it will affect her.
My DF favoured my brother (2 years younger than me) and did loads with him.
I've spent my adulthood thinking my dad is a bit of a twat and he wonders why I don't bother going to see him much.
Neither does my brother - so it did him no favours. Brother doesn't go because he's a self cetred arse who can't be bothered. I don't go because he literally spent my childhood making me feel he didn't give a shit about me.
Ask your DH if he'd like to look forward to that as they grow up.
I think this is exactly what occurs.
I worked with a girl early in my career who was very bright.
Her brother was the hugely favoured child in her home and despite this girl being well capable of university, her parents, particularly her old fashioned father, thought there was no point and insisted she did a secretarial course.
Her brother failed his course exams a few times and had to repeat, costing more money.
She did a degree the long way and worked so, so hard, eventually landing a very prestigious position in her early 30's.
She also married incredibly well.
She has NEVER forgiven her parents and sees them once a year briefly, they are not a part of her 4 children's lives.
Her brother eventually qualified but golden boy has never really amounted to much, certainly he has given a very poor return on the huge investment of his parents.
Her anger is that such was the favouritism that her education was not worth investing in.
Her father wasn't nasty to her, just completely disinterested in her, her future, and providing her with any opportunity to fulfill her potential.