Allan Gibson and family

I am trying to find all the partners of the Gibson siblings, I had found Elizabeth Gibson (born c1795) on the 1871 census living with Betsey Gibson, which I thought might be Elizabeth, wife of Allen Gibson - my 4x great grandparents. So after looking for a marriage between a Betsey and a Gibson son, the choices being Allan, Anthony or Joseph I found a marriage between an Allan Gibson and a Betsey Robinson in 1853 in Yorkshire. There was also a Betsey Robinson residing at the same place as Allan Gibson on the 1851 census, noted as being a servant.

The certificate has now arrived and it looks like I have found the right one. Age tallies as well as fathers details. Interestingly it states Allan Gibson residence was "the Parsonage, Dent", the minister at the wedding was John Sedgwick which I believe is the same person Allan was working for according to the 1851 census. He worked as a coachman.

Finding them on future censuses was relatively easy but Allan and Betsey weren't living together on either the 1861 or 1871 census. Allan was still working for Jane Sedgwick, widow to minister John Sedgwick on the 1861 census. The 1861 census shows that Betsey has now has two daughters Elizabeth (born c1854) and Alice (born c1856 in Dent, Yorkshire). Alice is still living with her mother on the 1871 census but Elizabeth has disappeared.

I then had trouble finding any of them after the 1871 census but I have found 4 deaths that might be theirs, Elizabeth aged 15 Dec 1869, Alice aged 16 Jun 1872, Betsey aged 49 Mar 1872 and then Allan aged 49 Mar 1873. I am intrigued now and want to know what, if it is them, they all died of so close together.

So I have sent off for the certificates and will report back when I get them.