I would be here all day if I went through the background but DH and I have been together 12 years and have a 3.5yo DD, he has a sister who has 2 boys (4 and 1). Historically had a lovely relationship with in laws until the kids came along and the favouritism started becoming obvious towards SIL older little boy, but for the most part I've bitten my tongue.
MIL has always looked after DD on a Monday, she told me before she was even born that this would be the plan - they live a 40 minute drive away, and I said are you sure you're happy driving to our house every Monday and staying there/in the local area until we got home. I leave the house at 8am, DH is gone by 7 and they said yes - and that's been the situation for a few years.
A few months ago, I was going to start sending her to pre-school a few days a week to get her ready for school. MIL was really hurt by this, begged to keep her etc, got really upset and so I said ok we won't send her on a Monday, it won't be a problem.
This moved along okay until SIL little boy started school in September. SIL works mon-wed, so MIL agreed to pick him up from school every Monday as they only live around the corner to avoid him going into after school club. She said they could still come to ours in the morning, but I'd need to pick up from theirs. This meant I was now finishing work at 4:30, driving to her house to pick up for 5:15 and getting home at 6. Ok - I could manage that. (DH finishes later, so it wouldn't work for him to do it - he has days off in the week where he does pick up/drop off at preschool etc).
She has now said this morning she has agreed to also have him every Monday in half term/summer holidays/Christmas etc etc, which means I now have to drop off and pick up as they won't drive that long with him in the car. So I have to leave the house around 6:45am to drive the 40 minutes to their house, then the 1 hour drive to work, then finish work, drive to her house and get home for 6pm. DH literally couldn't do it if he wanted to as he works long long days to allow for days off in the week.
Not only am I a bit miffed I'm now going to be doing this over all the breaks, but also that MIL begged me for this 1:1 time with DD, and she's just decided it's not that important anymore.
DH is equally annoyed as we could've just sent her to preschool and avoided all of this, but the space is now gone. We're seeing them on the weekend and I want to voice that I'm upset about it, but really what other option do we have - I just have to grin and bear it until she starts school.
YABU - Just be grateful
YANBU - I'd be annoyed too