Saw this tweet "Louise C asks, 'The W. Telbin who acts as a Servant in The School of Reform is mentioned alongside a second Telbin on another playbill. Are these related to the famous scenic painters, I wonder?' Theatre Royal, Hull, 1829" (https://twitter.com/LibCrowds/status/1280120562464014336?s=20) and couldn't resist the challenge. I don't think it's possible to give a definite answer but I think it's highly likely that these are members of the same family.
I'll admit I had no idea who the scenic painters were so I started with Google to see what information is available, the bios are fairly sparse but I found enough to see that the painters were William Lewis Telbin the elder and the younger.
Due to the lack of information I've carried out some quick searches of genealogical records (baptisms, marriages, census records etc), the British Newspaper Archive, and the British Library collection. What I found is that Telbin is fairly unique name which makes this a whole lot easier. I'll try to keep this brief but I'll include a lot of details here so it's easier to see why the probability is high (the main problem is trying to identify who the various Mr Telbins are on the playbill, although W Telbin probably is one of the famous scene painters).
Census records show that William Lewis Telbin the elder was born in the 1810s in Norfolk, but there is no christening record for anyone by that name. As it's such an unusual name there were only a small number of christening records for the Telbin family, John and Elizabeth Telbin had several children; Edmund Cain Telbin in Cheltenham in 1817, Rosalind in Stratford Upon Avon in 1822, John Nobbett in Scarborough in 1826. There was also a burial record for Elizabeth, a daughter aged 15, in Jersey in 1834.
Searching the BNA found a few references to a performer by the name of Telbin; the Sheffield Independent's 1823 review was a little unkind, 'Telbin’s Capulet was most foul, strange, and unnatural', but the Durham Chronicle in 1827 provided a helpful clue 'The Siege of Scarborough Castle,.. written by Mr Telbin, a member the company'. There is a copy of the script in the British Library collection and it shows that it was written by John Telbin http://access.bl.uk/item/viewer/ark:/81055/vdc_0000000303AE#?c=0&m=0&s=0&cv=5&xywh=691%2C589%2C2013%2C1070
The Western Times newspaper from 1874 provides another clue, 'London papers report the death of Mr. Telbin, an artist who had acquired great celebrity as a scene painter. Mr. Telbin and his father were members of the Exeter Company some 40 years ago', The playbill collection provides further evidence of this (thanks to the text searchable version of the playbills), a playbill from Weymouth in 1831 is 'For the benefit of Mr Telbin, Stage-Manager and Mr Telbin Jr., Artist', along with a playbill from Devonport in 1830 which advises that 'New scenery painted by Mr Telbin Jr', and a playbill from Hull in 1829 includes appearances by Mr Telbin, Mr W Telbin, Mr Telbin Jun, and Miss R Telbin. As a further connection to John and Elizabeth Telbin the playbills for the theatre in Jersey from January 1834 include appearances by Mr Telbin.
Although it's been impossible to find a christening record for William Lewis Telbin I have found a record for William Lewis Niblet, son of John and Elizabeth, christened in 1814 in Norfolk (it could be a coincidence that Telbin is Niblet spelt backwards but that seems unlikely...)
I'll end it there but what I've found so far has been fascinating!