The BBC have an interesting infographic showing the comparative family trees of the royal couple ahead of their marriage in a few days. Kate Middleton's family tree is interesting as on one side of her family are coal miners and general labourers up until the end of the First World War and manual workers up until the mid part of the 20th century.
It should be noted though that this isn't that unusual. The 1920s saw a great social upheaval with many families moving up (and down) the "social scale". Indeed some of this upheaval occurred in my own family. In the early part of the 20th century the Grants in Aston, Birmingham were fairly big wheels. They owned a bakery and had a rather grand house complete with stables, servants quarters (complete with bells), two sets of stairs et cetera. Where all that went is unknown, my Mum was too young to know what was going on in the 1930s. The Luftwaffe may have had a hand in it perhaps.
Mind you they still had some brass. It is a bit of a hackneyed factoid these days about the Queen's coronation and people watching it on TV in other people's homes but my Nan did indeed have the first TV in her street in Shard End (they moved from Aston after the war) and the neighbours did come in and watch the pageantry.