Expecting to babysit at the weekend

Your wife is entitled to a close relationship with her nephew and to help her sister out with childcare. In many families, outside of MN, it's the norm. You are entitled to decide that it's a deal breakers.
@DPotter why does the OP get to dictate what his wife does?

Yes your own can be worse! Relentlessly neverending

@sundaysitter never you would never want it reciprocated

what is it that is making you angry and who are you angry at?

Yep, I’m with you. A couple of much-appreciated hours here and there while they have a rare night out is very different to you giving up 9 hours of your Sunday at least one week in four so they can go to work. They need to source regular paid childcare. They are so cheeky for acting like giving up a day of your weekend is some kind of bonus / treat / luck for you!

They’ll no doubt point out they can’t work without your help and be devastated. However, sometimes CFs like them do need to bear in mind that they knowingly chose to have a baby while doing those shift patterns and don’t seem to have considered a work around for after maternity leave other than just assuming that you’ll do it. It’s something they should never have expectantly asked you to do unless you had already given very clear signs of enthusiasm about helping. Presumably you absolutely did not, but now the time to spell it out. How often on here do we see nice people roped into helping with things that only suit the recipient and which often become even more piss-taking with time?!

Disagree with you there. There's a big difference from doing the occasional baby sitting shift, but this is a regular and sizable commitment. There's a big difference between looking after your own child and someone else's.

Just because this poster doesn't want to babysit for his SIL, doesn't mean he's not ready to be a parent

Well if you all work shifts, maybe in the future would be a good reciprocal thing? I would agree to once a month? If your wife wants to do it twice you can stay at home.

and if you are seeing it as a chore maybe you aren’t ready for parenting! And perhaps your wife wants to practice

Will they be able to do something similar for you when yuh have children - babysit once or twice a month so it isnl reciprocal? Either for work childcare or for date nights etc?

You don't have to do it but you do not have the right to stop your wife doing it. You can explain how you feel and ask for that to be taken into consideration but if she wants to help her sister that's up to her. I used to drive 2.5 hours on a monday, mind my niece and nephew tue, wed, Thurs and then drive home and my husband never once tried to stop me because he knew it meant a lot to me and was incredibly helpful for my brother and sil but to be fair I gained the most because of the relationship with the children.

No chance I'd do this.

Tell them you'll look after him in extreme emergencies only, and at your house.

The cheek of it! They need to arrange proper childcare.

I'd book a few things in for the next few weekends. Nip it in the bud now before it becomes an engrained expectation

Now is the time to draw those boundaries! You will have to put some very firm boundaries in here.

Be clear with your wife - this is an occasional favour your offering - it is not a regular commitment. Make it clear to your wife you do not expect this to become a regular commitment. Fast forward to when you have your own child - will they return the favour ? My feeling is they will not.

I'd get some dates in the diary for going away at the weekends so neither of you are free to provide free child care.

Suggest they drop off and pick up the little cherub.. After all they need the favour...
Never get onto babysitting for family ime...blurs the lines...