Hi,
I'm in Australia too, it's tough searching from this side of the world isn't it
I have the Glamorgan censuses on Cd and ran a search through the 41, 51, and 61 for Isabella Morgan ( and her maiden name, but returned no results that matched her) , as that "Isabella" Christian name is the more unusual to search on,and should be the easier one to find among your Morgan family. I didn't search the 71 because the discs I have are not searchable by names of people on that one.
The only Isabella Morgan in the 51 census is a servant c1828 , and she is unmarried ( so if she was a crellin , that can not be her)
There are no Fred's , or Frederick Morgan's ( or Morgans) in the 51 either that I found that match up .
There are two Frederick's ( searching for fred the father ) who are married ( the rest are unmarried and most are too young) in the 61 census, none of them that I can see match up to yours, none have a son called Frederick Morgan, and none are married to an Isabella
The same goes for the mother Isabella crellin, or crellino etc ( or by her married name Morgan), I used a soundex search ,and found nothing that looks to match your Isabella.
so, I'd guess that they did not come from Glamorgan, as I found nothing in those censuses which look like a match for your family.
It may also be worth searching for "George Morgan" besides "Frederick George Morgan" in the 1881 LDS ( just in case the father Frederick senior or junior are listed by a middle name on a census. What I have found with some of my family when the son has exactly the same name as the father in the house, the son tends to be listed by his middle name on some of the censuses)
Hope that is of some help , perhaps someone with the other counties of Wales could look for you at them , and maybe even double check the Glamorgan censuses, just in case I have missed something with my search in the Glamorgan censuses of 41, 51 and 61.
P.S. I'm assuming it was Frederick junior who was born around 1852, or did you mean his mother was born in 1852? There are no Isabella Morgan's ( or crellin sounding names) that I found in Glamorgan in the censuses anyway, only one was a maid which I mentioned above. 1861 there was a child of a morgan family with the name Isabella..so that can't be her either, nothing that looks like the surname crellin either
