In Dragon Age Origins there is a somewhat spicy NTRS situation but its hard to explain without spoiling the ending.
Before fighting the final boss Morrigan (one of the romancable females and a witch) asks to knock her up because the child will prevent your inevitable death.
HOWEVER! You can refuse and suggest that she does it with someone else (either Alistair - a good friend or Loghain - a villain).
She complains but in the end does get knocked up by one of them.
And this can be done whether she is you lover or just a friend.
I did go through this route because it does have my favorite things. Absolute trust and a confident woman.
She does it to save you but you still refuse.
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