It's also the only type of nepotism which is absent from most other industries. In hospitality, for example, a husband managing his wife will be grounds for dismissal but in the railway it’s very common.
Don’t start me off on that one! I’ve come across it twice, one of which didn’t concern me directly, but the other example did, and it essentially led to a situation where there was an (obnoxious) abysmally performing manager who was subject to no performance management, and - worse - the usual mechanisms where staff could raise complaints against their manager were essentially worthless as in the first instance one would always be dealing with her husband. She was eventually ditched during a wider review when her role (and that of her husband) was declared surplus to requirements, they both went through the redeployment process and failed to find an alternative position so after the requisite time period simply rolled off the cliff. But this only after causing massive amounts of aggro for staff in the team. The manager concerned was next seen working in a clothes shop in Chelsea, couldn’t resist paying a little visit to the area some years later and dropping in to say hello!
The other example was a depot manager where the admin clerk was his wife, that was a grubby conflict of interest too, albeit unlike the first example there seemed to be some attempt at maintaining a professional distance.
On the wider issue of nepotism, I’d agree with the view expressed here that it isn’t massively widespread. For roles like driver the same technical test regime would apply and there’s no way of bypassing that. A family member would be expected to have some advantage in an interview as they would (should!) have a better knowledge of what the job involves, what the company does, et cetera. I’ve known this work both ways, some awful people who are frankly an embarrassment to their elder, but in the greater majority of cases there are also some pretty good staff especially drivers and signallers. You also tend to get a fair few cases of “father told him to apply just as a stop-gap, 40 years later he’s still there”.
It’s just one of those facts of life really, I don’t think the railway has any more of it than anywhere else.