Hello all, i keep banging at these walls in the hope that one day they will topple! So back to the Lynch's

I still have not managed to find them on the 1891 census, & i am also looking for some other details to add to this family.
Living with the family on the 1871 census is a Arthur T Lynch born Plymouth 1870, i can find no birth, death or any other record for him other than this census!
James R Lynch b 1875 Plymouth on the 1881 census appears he could of been born in Caistor, no idea why the family would be there, again no record of him after this census!
i've found a death for a matching Thomas Lynch b Ireland 1839, in August 1887 birth 1833 Devon. (different from the census records) A matching probate record says he was a Hawker which matches the 1881 census & says that he died in Plymouth workhouse 6/8/1887 he left £24 1s. Some of his children were in the workhouse on the 1891 census. Would he have been able to leave money if he was in the workhouse?
Hope you can help save some of my mysteries!