They were a travelling family so there are few records available.
I wasn't able to find a marriage record for them.
In fact, I have only been able to find them on census's and I was able to find the records for two of their children, Isaac Jr and Bill.
The place of birth for Gravelina, and all the family, vary from each record between Altringham, Macclesfield and Cheshire so I can't be sure at the moment.
Her parents were George Boswell and Louisa Sherriff.