Hi Rachel,
tried to download your file, but couldn't. must my firewall at work.
Anway, I assume you don't have any more info than you've given us.
You should really start by ordering Henry's birth cert.
Using FreeBMD you could then find the marriage of Henry's parents and order their marriage cert. That would then give you their fathers names. Maybe also their ages.
As they were already married in 1901, you should be able to find them in that census. Working back, you should then be able to find Henry Beynon and Margaret Killa in the 1891 census. I assume by then they were still living at home, hence you will then have the names of their parents (confirmed by the marraige cert) and their siblings. Also the address, which will make it easier to find the parents in the 1881, 71, etc census. And so on it goes. Ordering certificates, looking at census, parish records.
Hope this helps.
D