Summary Question: If someone is leasing land from another person with the same last name and is presumably the one living next door, does that indicate they are related like father/son?

Long Question:
I have a marriage record from 1855 saying that my ggggrandfather Bartholomew Donovan married Isabella Mylrae in Lancashire and that Bartholomew was born in Ireland. The record also indicates that he was the son of a John Donovan.

I can't find him in the 1851 census, although there's one Bartholomew Donovan who is living in the area but married to someone that I can't find a record of death or original marriage. When I look at the Griffith's Valuation, there's one Bartholomew Donovan who leases his land from a John Donovan that is (presumably) living next door. Is that an indication that that John and Bartholomew are related?

The short answer to your question is no, there is no 100% ironclad certainty they are related.

I was told this in a genealogy class. Even two people with the same name in the same location and called Junior and Senior or Beg and More may not necessarily have been closely related. Such suffixes may have just been ways to distinguish an older person from a younger person but do not necessarily imply relationship.

Thanks for the reply- Makes sense.