Thanks for bringing that to my attention, that'll require some major finagling. It seemed as though it would check each giver individually for blocking/unblocking the actions, but it is likely either the case of one overriding the other or checking both per stage then moving to the next. Does it do the same thing if you select them in the reverse order (non-related then related)?
That's a bit peculiar, as Incest should very rarely cause stress.
That code change sounds awesome, and I am very excited to have some modding help on dialogue and fleshing out areas like that. I'll look forward to it!