Last bit first:
It's all too common not to see a barrister until the day of the hearing. As the family member you refer to is obviously pleading guilty, that
might not be too important.
The judge may well read the pre-sentence report prior to the day of the hearing. He can also seek direct representations from, for example, the Crown Prosecution Service. If he did so, your family member's solicitor should be present.
When considering sentencing, the judge is given a 'starting point' and a range within which the actual sentence should fall (unless there are extremely exceptional circumstances). You can read the document which the judge will refer to, here:
http://www.sentencing-guidelines.gov.uk/docs/a ssault-against-the%20person.pdf
The most important part of that document is the table on page 15. However, you should note that the sentences referred to there relate to first time offenders
convicted after a trial. An early guilty plea should result in those sentences being skewed downwards.
Looking at that document, you'll see that there's a reasonable chance of a non-custodial sentence if the following three conditions are met:
1. No pre-meditation involved in the assault ;
2. No weapon used ;
3. No 'grave' injuries.
Otherwise a custodial sentence would seem to be almost inevitable. (Even if those conditions are all met, it would still be wise for the family member to pack a bag when he attends court. He should keep hold of it or, if that's not possible, hand it to a court official or security guard. If he gives it to his solicitor or a family member, it won't be possible to get it to him in the cells if he's 'sent down').
Chris