Family history: what you need to do is start with yourself, then the names of your parents with birthdates, then the names of your grandparents and dates and the maiden name of your grandmothers.
In this way you work backwards, getting confirmation with birth, marriage and death certificates as necessary.
When you get close to 1901 it is possible to use the censuses to work your way backwards, with the same system, and with the crucial certificates.
1940 and later is a little bit too recent to be publishing information on the internet, particularly as the people may still be alive.