Hi Anne
It took just a couple of minutes to find the marriage of a James Thomas Martin in the St Helier Parish index, Dec 1847 to Jan 1851 on page 98.
On page 98, there is only one Margaret and that is for Margaret Odgers. However, I need to check the certificate to make sure that is correct.
Working on the presumption that is the right wife, I can see the baptism of a Peggy Ann Odgers on 7th Jul 1824. There was no Margaret in St Helier from 1817 to 1838 so I assume that Peggy was the alternative to Margaret.
If that is the case then she had a brother called James, baptised 6th Sep 1818 and Louisa, baptised 25th Oct 1822.
Parents were William Odgers and Esther Dodge.
I'll get back to you when I've seen the marriage certificate.
Stewart