Hi Alan
I feel sure I have come across these chaps before... though I can't think why/where, however, I digress.
I don't think they are brothers, Evans being fairly common probably makes it nearly impossible to tell without something concrete to attribute. I assume Samuel is the main man in this...
2 family possibilities for Samuel (IGI submissions) may be more, but these appear closest:
1806 Denbighshire, parents: John Evans & Elizabeth.
1805 Denbighshire, parents: Benjamin Evans & Ann.
Samuel had been busy before the 1834 transportation, if it is the same chap:
1825 in Denbigh' 3 months for 'Larceny', no other details
1833 Oct 18 in Wrexham, Denbighshire. Difficult to work out what happened here, disch, looks like some sort of bail for £25.
If you have difficulty accessing any of these records let me know and I'll upload copies to one of my sites where you can download them.
Regards
Geoff