breathing unaided at 23 weeks is remarkable, and 15oz is not a bad weight.
It's a long haul when the babies are early, mine was 29 weeks, and usually they will come home at around the due date. Between now and then is a rollercoaster (it is later too). Bliss is great and there is lots of information there.
In the meantime how can you support your cousin and his girlfriend. Lots of texts, messages of support. Don't expect replies. I found one route of communication through one person was the best way. Lots of food , go to the supermarkets shops, cook food they just need to reheat. Offer to drive your cousin and his girlfriend to the hospital especially if she had a section. She is highly likely to be discharged a long time before the baby and will want to go back in a lot. If she can't drive that's a real pain.
As and when the baby comes home do the same things, cook, shop, drive.
Get your cousins girlfriend nice thigns for her - shampoo shower gel, choclate anything that makes her feel more human.
Remind them you are there for them, keep reminding them. Tell them you are thinking about them, often, and keep telling them.
Finally is money an issue. Its often a real financial issue to have a prem as you don't have time to save, you are on mat leave much earlier than you planned, there are additional expenses going in an out of hospital. If money is an issue try to get them whatthey may need (food again, stuff for the baby when it comes home - they won't have had time).
I'll keep my fingers crossed for you all.
xxx