The earldom is hereditory so on the death of the current Earl he was succeeded by the next in line, usually his eldest son (if he were still alive!). Francis Howe was the 5th Earl and his son the 6th. We have the 7th Earl in the House of Lords now, as it happens.
The convention was that until one became a Peer (the generic term for all ranks of titles that entitled the holder to a seat in the House of Lords) one was a commoner, and therefore those with political ambitions could offer themselves for election as members of the House of Commons. Whilst the Commons is technically the lower house, in recent times (20th century on) the govenment of the country is conducted there, with the House of Lords having a secondary role.
Some of the families have several titles, acquired in historical times and in the 1920/30 period the Earl Howe also held a Viscountcy in his family name of Curzon (not Curson as I wrote before) and although the sons of peers are common enough to be Members of Parliament, it was conventional for them to use one of the family's lesser titles as what was called a "courtesy title". Hence the man with the ERA was known as Viscount Curzon both on the race track and in the House of Commons until his father died when he became Earl Howe which disqualified him from membership of the House of Commons.
By now, unlike in Francis Howe's time, only a small proportion of the hereditory peers have seats in the House of Lords: in 1963 a system of "Life Peers" came into being so that people could be rewarded for their achievements with a seat in the House of Lords without their family benefitting for ever after (as before).
Hope this helps - it's an engineer writing it, not a professor of politics!
Mind works slowly at this time of night and Carnut beat me to it, but I'll let what I wrote stand!