The real issue is that for some reason one son feels that the other son was the favourite son and he was always the also run.
It doesn't mean that this is actually true, just that something happened that led to him thinking this. I had this problem with my sister. It was only after our father died we had that heart-to- heart conversation that addressed the issue, that turned out to be based on a misunderstanding.
You and the son who feels sidelined need to have a conversation with defences down to explain the past and understand each other and then go from there.
Alternatively, as there is not much time to re-organise this Christmas, grin and bear it and in January tell both sons what will happen from Christmas 2023, that you will spend Christmas day with each son alternatively. and Christmas Eve/Boxing day with the other - and stick to the arrangement
paying a teenager for watering
Fabric conditioners - are they a con?
I have a mobility problem and my husband's angry all the time