Annoyed with mum bringing sibling to playdates

To be honest OP, you don’t seem very nice

OP, your DC is three years old.
You talk about the importance of 1 to 1 time to strengthen their friendship, but at this age that seems more important to you than your DC.
They are still at nursery age!

YANBU if she is dropping her child off.

but you are very unreasonable if she’s staying.

YANBU about wanting to know whether she’ll bring the older sibling (even if she is staying). But why not just ask? (and accept the answer that she’ll have to bring both if she’s staying)

Ok but you don’t know their situation vs this other parent do you. The number of kids is irrelevant really. Could be 2, could be 5. My husband works weekends so I always have to take both kids to play dates where I stay.

Why are you so keen for your kid to have ‘one on one time’ at the grand old age of three? Especially with a child who you say is ‘shy’ so doesn’t sound like a very fun playmate!

You say you do other play dates so what’s the issue? Just stop inviting them and invite one of the others who don’t piss you off! I don’t get the angst.

I don't think they need it at this age. With respect, I think your expectations are a bit full on. Kids this age can be quite fickle with their friendships. If these are nursery class children, once they go into reception, you'll probably find that they mix and make different friends.

Why is it so vital that they have 1 to 1 time? They are 4. Does your DC enjoy the play dates?
Personally I think it's nice for kids,and good for them, to play with groups of kids of varying ages and siblings of friends are a good way of finding this -IF the children all get on.
So if this stray sibling means your DC is unhappy because they do want to just play with younger child, then you need a solution. If they are happy then it seems as if it is your issue - you have a specific idea of what you want from the play dates and it's not happening. Not saying you can't want a particular thing but if this little group works then I would look first the 1to1in no addition and somewhere else!

It depends on the play date.

"Let's meet at the park/ trampoline park"...I'm bringing the sibling!

But at someone's house I would ask (if staying) or if the other parent is taking them somewhere, then obviously no.

My DC are two years apart and this is very normal in my circle, the more the merrier!

If the play date child is being dropped off it is unreasonable for her to also leave the sibling with you.

If she stays it is unreasonable to expect her to be able to arrange somewhere else to leave the sibling.

Most parents would not drop at 4 y.o off for a play date, unless it was their sibling or very close friend of the parents.
Yabu and selfish. Your DC can learn to play with different children, including shy children. Your DC doesn't have to be the main character.

When my girls were younger , they’re 17 & 14 now , I always brought the 2 together , as in when F was smaller & I stayed at the play date with her , & R was always with me too, & same was done at my house with play dates, moms & siblings 🤷🏻‍♀️..
None of us ever minded, & everything always went off great , kids happy out with the company & same with us moms 😊

But might have a completely different home life! Perhaps the other parent is around at weekends? Perhaps the grandparents take them out for the day? You don't mention if this parent drops and runs as maybe her youngest is used to being left/having to slot in being part of a larger family so more confident.

She probably doesn’t have any other option. I wouldn’t bring my eldest along if I had other options, but on occasion I have had to bring her.

I mean this kindly, but you don’t understand it because you only have 1 child.

Offer to have the youngest over without her Mum, but appreciate she’s likely to say no if her child is really shy.

Have you asked her why she brings the sibling and to please not bring them anymore?

I've never looked at play dates as 1:1 bonding time. I don't understand why this bothers you so much. Maybe the child would rather have their sibling there. Maybe there is no alternative childcare. Maybe the parent is worried about the child being left alone with you. I think you need to relax a bit, playdates are supposed to be fun but you seem so uptight around it and you haven't given any explanation as to how it negatively impacts your DC having a sibling come along.

Yabu. You don't get to dictate whether she organises childcare for her other children and whether she's a single mum or not, you don't know her full circumstances. If it bothers you just stop arranging these playdates with her, they are not compulsory. My kids have gone to others houses to play but I wouldn't attend a playdate where I had to stay unless I was friends with the mum. My kids are too old for this type of set up now but with multiple kids I didn't always have a lot of free time or childcare to hand if my husband was working. Sometimes they would attend a friend's birthday party with a grandparent as that was the better option to dropping all my other kids off to facilitate it.

I think yabu on several counts.

It sounds to me like you are trying to use the younger child to facilitate something for your child (rather than it being a lovely relationship for all of the children).

You don’t seem to understand that not everyone is in the same situation…

Maybe her husband is busy at the time you suggest? Your suggestion that she coordinates two separate play dates at the same time for each child is frankly laughable.

You could just say - “my child would love some 1-1 time with their friend, if you prefer to drop your younger child off with me for a few hours I’d be happy? I know you have to juggle 2 so it’s tricky”