It all depends on the individual circumstances. In the following I will deal more with a situation that implies the topic of marriage. I understand your concept in a way that the "young master" still lives in his father's house and is dependent on his father and can be put under pressure by possible disinheritance. Whether or not the father will tolerate a love affair between his son and the maid is a decision you have to make as an author. In historical reality, it was certainly most often the case that the father did not tolerate a socially "improper" relationship, but there were certainly exceptions. In any case, it would be a literary cliché to portray the father as unchangeably stubborn. On the other hand, it is part of the author's duty to offer the reader conflict, so the father should in any case first put his foot down and then in some way be convinced that his son has made the right choice, that is, the choice of a girl he really loves. It would be more dramatic, of course, if the son ran away with the girl and renounced his inheritance, but later reconciles with the father, under any circumstances that are conducive to this, e.g. when he or the girl helps the father with a problem. In the event that the girl becomes pregnant and the son is in need to explain himself to the father because he already suspects him, the story could be developed in the way that the son convinces the father of the priority of love over a "proper" relationship. It would also make sense to involve the girl herself in this argumentation, so that she does not just appear as a dependent and passive object, but as an active subject, because one must not forget that the 1910s were also a time of feminist struggle for equality, which of course also applies to the mother of the son, who should also play a role in the conflict, preferably as an advocate of a love marriage.
Why do you prefer the mother to side with love marriage?
The most famous example in literary history of an unruly love marriage is the novel "Pamela, or Virtue Rewarded" (1740) by Samuel Richardson, which I translated into German in 2019. There, a young nobleman, who is however independent, marries a 16 year old maid (Pamela), with whom he is undyingly in love, but only after very dramatic developments, which seem to rule out such a happy end at first.
YOU translated it - in 2019.
It was famous... in English. At least into first half of 1800s - Charlotte Bronte´s Jane Eyre refers to Pamela by name and by references that betray familiarity with text of a specific edition.
That you needed to translate it suggests that there was no contemporary German translation?
Were there any German books about master/maidservant affairs, as in, popular books, which masters and servants would have read?
Henry Fielding said:
That every Maid Servant from what low stock soever she sprung, if she is pretty and modest, &c. has an undoubted Right to attempt to entice her Master to Marriage.
Henry Fielding said:
The Instruction which it conveys to Servant-Maids, is, I think, very plainly this, To look out for their Masters as sharp as they can.
Henry Fielding said:
If the Master is not a Fool, they will be debauched by him; and if he is a Fool, they will marry him. Neither of which, I apprehend, my good Friend, we desire should be the Case of our Sons.
coralray said:
I also understand that a powerful gentleman could get away with sleeping with whomever he wished,
Not quite. After all, a powerful gentleman cannot get away with violating another powerful gentleman´s wife or daughter.
And a heir is a gentleman, but not really powerful - because it is the master who is powerful.
There were several options which may happen if a servant was compromised with a master - or master´s family member. From worst to better:
1) As you suggest, fired with no assistance
2) Sent away but paid off to avoid a scandal
3) Upgraded from servant to kept mistress
4) Upgraded from servant to wife.
A master who was his own master could marry a servant. "Get away with"? Marrying below his rank meant giving up social connections that an equal wife would have brought, and might have affected career prospects, but after Napoleon generally did not affect already inherited wealth.
A master could do worse than marry a maidservant - 18th century Englishmen used Pamela as reference for abuse, but they acknowledged and pointed out that Fanny Hill was worse. If you do not get the reference, Fanny Hill was a literary character who before marrying a gentleman was a prostitute.
Now about parents... If they were concerned about their son debauching a maid, there would be questions. A young adult bachelor might get involved with other women below his rank - prostitutes, or actresses/courtesans. At least some upper class parents were reported to prefer a servant to a courtesan - a courtesan living outside the household and free access to competing admirers would have been harder to discipline and potentially more expensive as a kept mistress!
And there would be issues as to who exactly to blame. If son was involved with a maid, was it a case of an entitled brat abusing a vulnerable girl? Or would the parents see the maid as somehow seducing/manipulating the boy?
As for getting naked together, would they need to? In 1912...1914, were maids wearing underpants, or was it just a matter of lifting her dress?