Hello @Jimbokav1971
Using the example you posted of 'Fotheringhams'.
Andy Fotheringham was born in Alloa on 10th May 2009 and was Scottish only.
John Fotheringham was born in Alloa on 30th Dec 2008 and was Scottish only. - this is 6 months before Andy, so there is no biological way they could be brothers
Matt Fotheringham was born in Alloa on 9th Feb 2009 and was Scottish with Irish as a 2nd Nationality - different family due to different nationality.
So while these 3 people have the same surname there's no biological way they can be related (except for half brothers I guess, but we don't have that in game). A lot of the names you've listed are very common surnames and, if you play for a significant amount of time, you'll see them pop up more.
The Father/son/brother thing is VERY rare in FM, as it is in real life. But it is still in game and still generates, it's just very, very rare. (You can see this example found on Reddit recently.)
If you are using a 3rd party Database then that could of course have an impact/affect the game, especially if it's changing core parts of the DB.