I can't have both at once

I have had the two DGS together since the youngest was about 8 month, however I do have a fairly high tolerance for noise and mess so can appreciate that others might find it more stressful.

I do think they respond well to the Grannys' Rules approach. It is a treat for mine to share a bedroom, so they tend to excitement rather than fighting, but are aware that the ground rules are firm and unwavering .... chat is fine, but if there is any racket after lights out, they will swiftly be put in separate rooms.
They are usually good.
apart from filling my bed with crumbs from morning tea and biscuits

This is a tough one. We also much prefer to have them one at a time, or even "just" 2... When we have all 3 the dynamics are tough as they fight a lot when all 3 together but MUCH less when only 2. Of course one at a time is a real treat, but then it doesn't help DD that much!
The GCs are starting to understand the value of one at a time quality time with us, and even demand their rights, as in "L was with you for x hours yesterday, now it's my turn". My big treat is to have the 9.5 year old DG (going on teenager already!) for time alone with me. The kids very rarely sleep over (they live 5 mins away) unless their parents are away, but she often comes over for supper and bath time in peace and quiet, including me blow drying her hair for her - it gives us both a huge amount of pleasure

I'm not sure opting out is a good idea. It takes a village to raise a child, they say, so maybe you could try to encourage them to be friends while they are with you thereby helping the parents.

Anyone else feeling sorry for the younger child?

"Dgd likes attention, snatches his toys and ruins his games"

Chinesecrested your little DGD has never had an annoying older sibling who had interesting toys or the same undivided attention DGS had. She has always been smaller and it appears she has to fight to be noticed. She sounds like she needs the attention!

You have to do what you can cope with re overnight stays but I think it would be worth having a go with both ..then move to taking turns if it turns out to be too stressful. Your DGS is old enough to appreciate that far more than his sister! Maybe his special job could be to help her manage the overnight treat!

merlotgran I have both my grandchildren to stay together...but for the OP it seems that one at a time would be better for her! "The Lion King works in our house

I think notanan2 is talking a lot of sense.

We've said maybe when she's a bit older...

If you had DGS @ 2.5 it is disingenuous to say that DGD is too young to come.

You are at risk of ending up unwittingly preferring DGS simply because he is the familiar one, and it becomes a viscous cycle where DGD is always "more difficult" for you simply because you haven't invested the same time learning her ways that you did with DGS.

Please stick to your guns re alternating.

Its okay for them to learn that its not always their turn.

Its so common for grandparents to favour the eldests simply because they find it (understandably) hard to have more than one and they are used to the eldest but it has an effect on the siblings relationship with each other and is upsetting for parents to see their younger child "rejected" even if that is not the intention.

You are not unreasonable to not have them both, but if you had DGS @ 2.5 you should try to have DGD now.

You will have to relearn everything ad having her won't be the same as having him, they are different. But once you get used to her it will feel ad natural as it did having dgs.

I had that problem as well Merlotgran why can't they all be the same.

I had three staying over as well in a small house. It was wearing at times but they were only there for short periods so I could see light at the end of the tunnel. I once had to look after a friend's five boys for a few days, that was exhausting.
I stayed a few days at my daughter's house to look after three children, three horses and a dog. I think the animals were easiest. My grandchildren are all grown up now so enjoy the time you have with them it goes so quickly.

Crumbs. I'm finding some of the above posts surprising. I often had three DGCs staying over when their parents went away. No fighting, lots of fun and games and yes it was exhausting but there was always a video of Black Beauty to put on for the umpteenth time when everyone was flagging.

I think the only things I found a bit of a challenge were flipping car seats and their mechanics.

And be firm!

When I first started caring for two of my GC I said quite clearly that we loved having them but that we could only do it one at a time; so my DD arranged it so that one was with us and the other at nursery (now school for oldest) - it meant a bit more driving for her, but we were able to truly enjoy whichever child we had with us and make them feel special; and also we did not get totally worn out.

They are a bit older now and we occasionally finish up with two in the school holidays; but being older they are more sensible now.

I think you should tell your DD/DS that you want to have them one at a time.

I think you are entitled to have the DGC separately to keep the peace. My sister and I fought all the time. We also played together. Our gran was exhausted by us as we often spent entire summer holidays with her. We parted as we got older and made our own friends but I love her dearly and we still talk for hours on the phone. I want my adult DC to keep close.

We hardly ever have ours on their own so it's a treat.

Our DGS age 10, on his way home from a birthday outing with us told me what he really wanted was to have both his parents to himself without Her, meaning his little sister. She adores him and always wants to tag along.

I don’t know how to answer you really Chinesecrested except to say you know the best way to handle things for yourself and we are all different.

As our own small children didn’t bicker/ argue/fight ( except maybe the odd time) we were bemused by our DGC, they constantly do and yes, it’s very wearing.
They do this at their own home and also with us, but only want sleepovers together ( go figure, as they say.)
I think ( hope) they will grow out of it as they develop their own friendships outside the house.

I think you should alternate visits. Your grandson is perfectly old enough to understand taking turns and fairness and if he isn't good at it he needs to learn!

I only ever had both my grandsons together once.
I couldn't stand it!
The fighting was constant, and it wore me down.

We don't have both GC together because they fight and even though they have their own bedrooms they still carry on.
During school holiday eldest stays with us and youngest goes to holiday club. Every once in a whole the youngest visits but asks what her sister did and had to eat so that she can have exactly the same.
On their own they are no trouble at all.

I don't think you're being "heartless," at all! You need to arrange the visits so they are enjoyable for both you and your gc. If alternating them does it, then that's what you need to do. (I am not clear on whether or not that's what you're doing or if you're just taking dgs, period.) No matter if he's "horrified" or she cries. I feel for them, but they react that way because they can't imagine how this will work. Soon enough, they'll see that they both are being treated fairly and are having more fun this way. Imo, it's up to the parents to deal with the bad reactions by distracting them with some fun activity at home. They probably can do this quite easily, even with the five-year-old.

Exactly what nonnie said!

We have 2 together quite often and it's rare to get a whole night's sleep but it's only one night!

Nonnie has said exactly what I was going to say.

I don’t have my one year old grandson and my two year old granddaughter together because it is exhausting. You just need to be firm and say no. Also, I prefer having them separately because I can give them my undivided attention.

At 2 1/2 she is old enough to know that different rules apply in different places. If she goes to nursery she will already know that. A couple of visits is all she will need to understand what is acceptable in your home and will respond accordingly.

Your GS is also old enough to understand fairness so it would be fair to have them alternately.

It sounds as if you might have a bias towards your GS, do you? Children soon pick up on these things.