If that person was SEN, sibling etc, surely they would have got their first choice?!
It doesn't work like that. Most schools have taken away the sinking link now. We did double school runs for six months before we won our appeal to get DD into the same school as DS.
Distance thing: Well, it depends, for instance where we are it doesn't matter, if you're first on the list you're first on the list, and if a space becomes available in the relevant class then the first on the list gets it, whether they live two doors down from the school or 20 minutes away. This can go up and down all the time too. Looked after children will always take priority, and rightly so.
There is no linkage from the nursery but it does say it should go on distance (straight line)
Its not about the link though. If the child has any SNs for example it will be deemed as the school best to suit his needs. Distance doesn't come into it. There was no linkage for DS. BUT he has SNs and the school we applied for was the one we felt could best suit his complex needs. We were right too. They are absolutely brilliant with him.
If you can afford it, have a chat with and then hire an education solicitor who'll probably know more about the school etc. When we hired ours, it turned out they were doing a full week of appeals for the same school and every single one was allowed 
Appeal, but grab all the facts first and at least then if you still get told no you know you've tried your hardest.