there is just one thing in particular im confused about in all this games with families. why are the kids always uncomfortable when their parents are half naked. this is just a normal thing everywhere. even kids in their preteens play with their moms boobs once in a while in a motherly way not in a filthy way and that never arouses anything. and the massage thing family members give massage to each other almost everyday after hard day that includes children giving massage /not the nuru kind ofcuz/ to their parents and that is also one way to learn about human anatomy and muscle structure and how to releave the off stress and in some emergencies it helps alot. but in these kind of games it is kinda taboo and even looking at their parents or touching them is taboo that i never understand
No, that's not "just a normal thing everywhere". It sounds like you grew up in a backwoods/hippie commune and assume the rest of the world did as well.
When most of us in the real world see our parents half-naked we think "eww, gross!", not to go up and start massaging them or playing with their boobs. Some of us even go to this place called a "school" where we learn basic skills like grammar and punctuation while meeting other people and learning what is normal in society.
To answer your question, if it is indeed a serious question and you're not just trolling: the characters in these games act this way
because it's forbidden. They are manifesting sexual desire towards family members that they've never had before or at least they kept those feelings repressed. Having them eventually break this taboo with characters far hotter than any of our actual family members is what makes it an enjoyable fantasy without any consequences like retarded, Hapsburg babies.