Being trained as a knight and being knighted is two different things. An 14-year old boy might be trained as a knight, but he isn't very likely to have been knighted yet.

Other than that, customs will vary between nations, some nations don't even have knights.

I presume you mean by your question that noblemen should have access to Martial Abilities. I would say, not necessarily. The younger sons of nobility were often trained for the clergy, not as warriors.

It depends on where in Mythic Europe you are. In some places of historical Europe, by the thirteenth century it was already becoming possible for a noble to avoid providing individual armed service to his feudal lords. Sending a contingent of men-at-arms was enough.

That said, I don't see any harm in letting Gentleman characters learn fighting skills as a house rule.

//Actually, I wasn't thinking so much about Martial Abilities as I was a Gentleman's role in medieval society. As you point out, those younger sons destined for holy orders would hardly have to worry about not having anything to do, and knights fight for their overlords and take care of whatever land those overlords see fit to grant them, or protect their castles. But what kind of role does a minor nobleman who isn't a knight or a priest play? //

Depends a LOT on the spesific nation you're from. One could be a Saracen, studing art and culture. One could be a the son of a nobelman would has not sworn fealthy to some overlord.

// But what kind of role does a minor nobleman who isn't a knight or a priest play? //

If I had to generalize, I would say he manages his estate. Remember that a nobleman collects his income from peasant tenants. Managing the estate does not to me sound like a hard job, so I think the typical minor noble would have lots of free time for hunting.

Typically this sort of noble was a hanger on at court.

He might also be the baliff of a castle or some manor. He does not have any claim to the land of course but he would manage the estate. And that would likely leave him with not much time to go hunting in all frankness, or if he was hunting it would be for food. He would be quite busy...managing an estate was not a trivial task.

He might be given some sort of post in court...the dresser to the king, the royal somesuch. Look in Chivalry and Sorcery for the court posts if you have access to the books and you will see where a lot of nobles ended up.

But for this to happen he has to have a fairly high status to begin with, so you might imagine the third son of the duke ending up as a "gentleman" but not a knight...this is not likely to happen to the son of a hedge knight or lesser baron. It is possible though that a guild member might actually be a "gentleman" (of noble birth) depending on where you are, and when you are.

Hope this helps.

Whether every 20ish nobleman must even aspire for one of the two categories cleric or knight is dependent on the time and culture of your campaign.

I would e. g. suggest to treat Irish filid and brithemin (forming together the aés dana) as gentlemen - though none of those are clergy or squires/knights.
Even in Carolingian France allodial landholders might be considered nobles, but not train as knights if they hold no feudal allegiance - though such a position would be rather precarious and unstable. (See e. g. Marc Bloch, La société féodale, Vol. II, book 1, cp. 1.2).

Kind regards,

Berengar