I don't think Tom Holroyd is related but can't prove that for certain I just can't see any evidence at the moment pointing to him being a relative. I'm not a Manx resident but one useful place over there I've used is the probate registry where they have the more recent wills. You can find further information about families through looking up wills. When I was last over there we got to see the will of a relative that appeared to have forgotten us in their will. We were always curious about her final years and who got what so we had a good free nose and then paid for copies of the bits we wanted copying. We've never had much luck with wills we could have had a house in Malew Street Castletown but it went to spinster daughters rather than the eldest son. Here's the probate registry information link:-

www.gov.im/about-the-government/departments/economic-development/central-registry/deeds-and-probate-registry/