I have two DC and live ten mins away from dmand dad. I see her most weeks and phone 2/3 times a week or more. My brother has three DC and is married lives 20mins away. He sees them every 6-8 weeks, on the whole rarely rings. He is crap which is fine but my fm won't ever pull him up on it. Yesterday I phone dm and suggested we went bowling together me, DC and my parents. I suggested the time but mum said "oh your DB might pop in. We have not seen him for 4 weeks." He had not rung to say this might happen btw. So I agree to try and get an early slot but it was fully booked so I phone mum and say we will pop over anyway for a visit.
Anyway did my DB ring? Did he arrive? NO. So once again I'm sidelined and my DC for a non show which wasnt even arranged in the first place.
This is happening all the time. It happened over Xmas plans too
Ive got to the point now where I want to point out that though I understand she wants to see him and his kids she is treating me and my family like second best. I'm the reliable one but get kicked in the teeth all the time.
I have no wise words for you, Madeye, but do sympathise. In my experience the sibling who is more readily available (whether due to geographical distance or whatever) is regarded as run-of-the-mill, expendable and pretty second-rate, whereas the other gets to make Guest Appearances and the red carpet is rolled out! It's not just my experience - several of my friends have been through the same thing.
I'm guessing that the answer would be to be less available and so increase your perceived value, but TBH in my case (very elderly mother with little going on in her life) I can't bring myself to do that. It sounds as though you're planning to have a conversation with your DM; I'd suggest that you pick your words so that you're not bad-mouthing your brother, whilst still putting your point across easier said than done!