not to help BIL with the kids while DSis goes away for a few days?

but would you ask a family member to come and stay so that they could look after the children because you can't cope and wouldn't be able to keep the house tidy?

Haha nooooo

She doesn't have to ask another man. If BIL wants the help, he should be asking for it.

As for not wanting the house to be a tip when she gets back, my advice to her is that if that is the case, to turn around and walk right out again. Tell him she won't be back until he's got the house in the same shape that she manages to keep it in.

Lord above - can he not do this? Is it so hard?

Say no and explain why. He’ll never appreciate everything that your sister does for their family unless he has to cope on his own for a few days. In my opinion, it’s very important that you refuse to help.

No way! Do not encourage BIL to continue to be useless. If DSis can cope, why can't he?

Why did I ask how long is the trip? because 1 night isn’t very long to manage on your own. If the trip is 5 days or something then I would really appreciate family taking DS so I could exercise in that time.

I'd go but then take on a purely management role eg 'BIL, make sure you pack nappies in the changing bag' 'BIL the living room needs hoovering' 'BIL, the baby needs changing'.

In your shoes then it would be a hard no from me. Why did he have 4 children if he can’t actually care for them?! It will do him good to stand on his own 2 feet. I’m guessing he goes away more than your sister

Ffs, women to do childcare and housework because poor man can’t cope.

If she is seriously worried that the house will be such a tip because she married someone so useless they can’t tidy up and look after the kids, then she should stay at home. This isn’t your problem to fix.

He will obviously try and sleep with you, don’t you know on MN that always happens? 🤣

I know a divorced man who never has all four of his children at once during his weekend contact time. Apparently he can’t manage all four at once, even though his ex-wife lives with all four practically all of the time.

why?

but why have kids with an idle wazzock no matter how many you do or don't want?

How long is the trip? We only have 1 child but try hard to maintain our own interests so if DH goes away for a weekend I try and get family to help on a Saturday morning so I can still go to parkrun. Is there something like this you can offer - take the kids for a couple of hours so he can go cycling or something. This is the sort of thing I would offer -
no more.

Did your sister harass him into having four kids or was he happy to go along with it? if he was leave him to it, if the reason he’s got four is your sister I might consider it if I wanted to help her.
We have two kids as I know 3 would have tipped me over the edge!

I just said do him a list. 'pick up all the stuff on the floor and put it away. Look at the floor, if there is something on it that's not furniture pick it up and put it away. If there is something on the kitchen bench put it away. Wipe the bench. Wipe the sink. Vacuum the carpet in these rooms. Clean the toilet.'
I wouldn't do it for him either.

well no because he would guilt her back

Why doesn't she hire a nanny for the time she's gone and a cleaner for right before she gets back?

She seems awfully entitled to your hard work on top of your own life.

What, no time away from your kids at all until they are adults?? 🤣🤣 hilarious. Both parents present at all times to hang out with the kids? Is that really what you do? How old are your DC out of interest?

Agree entirely. He doesn’t mind going off on his own (whereas his wife clearly does have concerns), so I suspect it would wash over him.

This. All. Of. This.

Weaponised incompetence. He can be left to cope just fine, but he doesn't want to so he'll make a crap job of it and your sister will be left to deal with the fall out.

Not your problem. He needs to be house / life / adult trained.

You’ve ended this paragraph by saying he needs to learn by doing it but started the paragraph saying how the OP should write out a detailed plan of his use of time for him which is completely contradicting the statement of saying he needs to learn by doing it himself.

Im sure this man child has a job at which he has to think independently and take responsibility for something or someone and I’m also sure this man child copes perfectly fine when it comes to planning one of his many cycling trips.

It’s funny how he only becomes a useless human being when it comes to caring for his own offspring and home. It’s called weaponised incompetence. He doesn’t want to be responsible for looking after his kids or home so if he does a lazy and bad job of it he knows he won’t be asked in future. It doesn’t meant he isn’t capable.

No one loves "coping" but everyone does. He can, he just needs to be left to it.