Hello Julia - I can see why you feel slighted but it may be that son 1 has just one spare bedroom which if you sleep in, could not allow for any doubling up of guests. If, however, his wife's family come, they may all be sharing. So, if you were their guest they would need to find accommodation for a family, whereas if the 'family' is the guest, it's easier for them to secure accommodation for you with son 2. I would go along, and enjoy the event. It's likely that if son 2 is giving you his bedroom, there will be some conversation between the two of you about this, and you may be able to tease out of him the issues that were discussed between him and son 2 when the accommodation arrangements were made.
SNP and Greens end coalition deal
Scottish political mess. Is Devolution working?