Hi Lesley,
Just to follow up on Jean'd post, due to disclosure rules, you cannot look at birth certificates that are less than 100 years old online so 1905 is the limit on the site. Similarly, you can only look for marriage certificates older than 75 years and death certificates older than 50 years. So once you know his parents, their marriage certificate will most likely be old enough to be searched online.
Good luck with finding your relative
Cheers,
Clare