Am I U to feel second best

[tiredoutalways]

I probably am but this has niggled away at me for so long I think I have lost perspective (have NCd)
I live in the same geographical area as my parents and 2 siblings.
My DB works away and mum started up an arrangement with my SIL where she would have her and her 3 kids for tea every week, she also collects my Dsis children from school another day a week and feeds them both and my DSis when she comes to collect.Recently my parents have started to become 'older' and find it hard to cope with the boisterous grandchildre, and has recently asked if my DDS 10 and 12 can come to tea on these days too.Their cousins are much younger (4 to 7 yr old girls)and my girls especially the 12 yr old are very very good with little children and it is clear that they entertain them while mum gets on with the tea and then the clearing up.
If the grandchildren don't come for any reason on their days (and my SIL is prone to cancel at the last moment) , then mum just cancels my girls too.
I probably am being unreasonable but it would just be nice if occasionally she could have my girls just for their own sakes and not as baby sitters.My eldest girl has now cottoned on that is why she is invited.Also I feel a bit hurt that she invites my SIL and Dsis to eat there when they collect their DC, but NEVER asks me.
Another time I was really poorly and asked if she could have my 3 yr old for the afternoon and she said no because she was going to the dentist.Later on my SIL rang up and said could she have their child and mum said she didn't like to say 'no'.It isn't helped that my SIL looks down her nose at me and will only speak to me (or my mum) if there are none of her friends there.

I would feel hurt too and a bit PO that my children are being used in a way. My DM does similar with my 2 sisters and their children. Their children are younger than mine and I know that makes the relationship slightly different but it still hurts x

Could you talk to your mother about it?

I get absolutely what you are saying about your girls being used as babysitters.
One of my BIL, having had no interest in my dc, found that both my girls were very good with small ones and suddenly my girls were invited to stay and come over etc.
Then came the point that they requested when staying with my pil that one of my girls could come and stay at the same time. Pil do have my girls to stay, but half the enjoyment they have in going to stay is that they are for a short time the only one and they can do a certain amount of choosinng what to do etc. Somehow I've just never managed to coordinate the timing.

As it's your dm, I would start of by telling her that your girls feel like they're being used as babysitters.
It may be that she thinks they wouldn't want to come on their own, simply because they don't. So tell her that they would love to come and have tea with granny on their own.
Perhaps invite her to come to yours too-would they like to cook granny's tea for her? My girls would think that great fun.

The dentist thing may be just the way you put it.
"Would you be able to have my dc for the afternoon? You don't have to but I'm not feeling too well?"
"I'm absolutely desperate, I can't find anyone to mind my dc today, I've asked everyone and if no one can have them I'll have to cancel it, and I've been waiting weeks for this to come up..."

Some people are very good at sounding desperate like the second example when their actually having their nails done.