‘you've got 2 kids who are mobiles and your brother has one docile robot baby’
And therein lies the problem. Some people only feel secure in their own parenting style by putting others down.
You haven’t done anything wrong OP.
Neither have your brother and his wife.
If your methods work for you and your dh then that’s all that matters. They don’t work as well for the grandparents but so what? They aren’t the parents. There’s a big difference. And I totally get why, if you’re babysitting, you feel far more comfortable caring for a child who is settled and contented, rather than one who is unsettled, fractious and can only be settled by its mother. That’s plain common sense, it doesn’t mean the grandparents love your kids less.
OP- as an ‘oldie’ with 3 adult children in their 20s - can I let you into a little secret?
My 3 children each chose to stop bf at different ages. They each slept through the night at different ages. They each started childcare at different ages- dd was 12 weeks and actually I didn’t work regularly with my dc3 til she was about 14 months.
Guess what? They are all happy, secure adults. If you met them, you wouldn’t be able to tell who bf longest, who slept through earliest.
IMO a lot of parental pressure is self imposed when parents (or more often, mothers) do things a certain way expecting to have ‘better’ outcomes.
Honestly, apart from a small number of things where there’s cast iron proof (eg benefits of bf) there really isn’t any point in thinking one thing is better. And if you can’t bf, or if to do so would negatively impact on your wellbeing then ff is the best option for you anyway.
If a mother wants to go the whole attachment parenting hog, wear their baby, sleep with their baby, never put their baby down- fine.
If a mother wants to go away for a weekend leaving their baby in the capable hands of its father and granny - fine.
It’s a very narrow minded view to think that one particular way is going to guarantee a happy balanced child. Parenting is so much more than that.