Umm... it is often important to separate the known facts from some speculations of course, and I encourage you to consider obtaining the official transcriptions of those two marriages from 1864 and 1865 to then be able to seek out the original parish registers which will have all the details that the brides provided about their own parents and themselves ... the info includes Mother's maiden name and can often include any other names she had become known by .. this then helps you research back a generation on those parents ...
Re James arriving with wife who dies in Quarrantine... he and that wife had 3 children, then he marries Catherine and has 3 more children before he died in 1849. What ship did he arrive on, where and when... what info did he give when marrying Catherine ... was he noted as a widower, what was her status?
JM