someone Please could tell me how do i unlock them? i have finish the game 5 times now
Firstly you need to have all the 3 the girls at max in their affection level and then do this:
Give the girls the 2nd item that sells the guy in the gym at night (he appears in the 15th day if I'm not wrong) to improve their level of awareness, give them 4 or 5 of them to level up at least to 90% or more.
To unlock the 3P skill you need to have sex with your blonde cousin near the blue hair girl and turn off the skills of silence in order that she can heard you, she will come in and that's all.
For the 4P skill is almost the same, improve the level of awareness of the aunt at 90% or more (and icon of a bomb will appear above the bars in the right panel when you have sex near her) then have sex with your cousins with the 3P skill near your aunt and she will heard you and enter in the room.
As a side note, if you improve the level of awareness of your aunt and do something with your cousins near her when she's napping, some dialogues will appears.
Also, if the level of awareness of the aunt or the blue hair cousin is too high and you make to much sound while having sex with them (whichever the case) the game will end.