Both need a certain amount of purple hearts, but the HJ can be triggered by being caught using the sisters panties while shes in the bath (if you peek first THEN interact she'll always catch you before you blow). the BJ has 2 different triggers atm, but both start with the pink candy: theres the normal (sitting) version where you simply give the candy and spam interactions until she goes to the toilet, and the cockroach (squatting) version where you have to look around in the toilet after returning normally, but before making dinner - if you return early through the south exit you wont get to explore the toilet first, so if you want to skip having to actually explore you should use the door. The Doc says theres a lying version, but I havent found it and theres no promo art so i think its safe to assume that its just not implemented yet. I also have never been able to trigger the squatting version of the BJ event other than through the cockroach trigger, which you can only get once so id reccomend saving before you do it.
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you get it from the demon shop keeper, the one that moves around day to day (but shes usually either in the starting area, or the tile to the right). you can either pay for it or trade a salmon, but at least prior to 1.2 its random which candy you get - pink is horny, blue is sleepy, and green isnt implemented yet