pallbearer
That's just not true. By that logic if I slept with my doctor,
illegal, against the hypocratic oath. Red herring
Depends on the insitution and if they have control of your grades. Shady ethical ground. Red herring.
Only if your brother, his wife, and you consented to the act. Also red herring
Generally, illegal, red herring
Illegal, and unethical, red herring
Red herring
pallbearer
my best friend's boyfriend
Only if you, your best friend, and the boyfriend consented
Red herring.
If you and the ex consented, also again red herring
Children cannot consent to sexual activity, stop being hyperbolic, also red herring and straw man.
pallbearer
it would be okay so long as it were consensual. That's just not true, and it's illegal for a reason- because it crosses ethical boundaries.
CORRECT, but with the information we are given, there is no ethical breach with some 40yo banging some 20yo. Which is why all of the above are red herrings and straw men.
There is age difference, sure, but we haven't been given any info OP's dad wields power/authority over his lover (which would indeed make it unethical like your examples of student, teacher, doctor, and lawyer). It may squick you out but its not illegal, or inherently unethical. Until we are given info of possible ethical breaches there are none in my eyes.
pallbearer
OP is CLEARLY being hurt by this. This affects their entire family, not just the husband and wife. It's selfish to think otherwise.
The OP is also an adult, or near adult child. If the OP has problems with how her parents are configuring their sex life, she can kindly ask them to not talk about it around her, or put on her big girl panties and deal with the fact her parents are engaging in consensual non monogamy.