I'm not a parent yet and still in my 20s. I was wondering if it's ok for a kid (between the age of 2-8 years) to watch his parents kiss and romance with each other. By romance I mean holding your partner's hips with your hand or stare at each other while standing close to each other or anything else that isn't too sexual. Would this affect the child in a negative way?
From everything that I can find online, it is a positive thing to show affection in front of your kids. It models affection to your children, and it makes them feel more secure https://www.whattoexpect.com/news/first-year/how-much-pda-okay-front-baby-kids/
My own experience agrees with what I have read. I don't think I ever even saw my father and mother kiss until I was well into my late teens. They never showed any affection, never held hands. Of course, the problem was bigger than just their relationship. Once we grew too old to walk on our own, my siblings and I were never hugged or kissed. It wasn't that they were neglectful; all our needs were taken care of, my mother made sure we ate healthy, we never lacked for all the practical necessities. But affection was never expressed.
It affected us all to varying degrees. I understand from an intellectual perspective that hugging and kissing is healthy, but I am not comfortable with it. My daughter is a hugger, and it took her nearly ten years to train me to hug her. My son, who is more standoffish, gets hugged by his father when he needs it but the few times that I have hugged him it feels so weird and wrong to me, because my instincts were so messed up, that I just can't bring myself to do it often. I try, but it feels so awkward that he senses it and now that he's a teenager it's a little too late to change those patterns.
I wish that my parents had hugged each other, and us, a lot more. Please show your children that there is nothing shameful about showing affection to those you love.
I have one fairly vivid memory of an insight that I gained from my mother. She was watching one of her daughter-in-laws stretched out on the floor, and her six year old was sitting beside her, playing with her hair and snuggling. My mother was very upset. Offended deeply, as if they had been doing something shameful. When I asked her why it bothered her, she was confused by my question. I realized that it was an emotion from such a deep place inside her that she couldn't even verbalize its source. Then it occurred to me that her own parents also completely lacked affection towards each other (they slept in separate beds for all the time that I knew them, and most of their interaction involved nagging and criticizing each other). To her, as to me, such things feel wrong. Almost shameful.
What kids learn from their parents, they pass on to their own kids. How many generations past led to my inability to allow myself to feel affection toward my children? It took a little girl with a great deal of innate wisdom to break my cycle.
If anything I believe it would be positive, although I don't know of any studies on the subject. Children learn how to be adults from the adults around them, so seeing what real romantic relationships are like can only be a good thing.
What happens if they copy you while playing house? That should give you a clear idea of where to draw the line.
If they express discomfort then stop.
The other answers give great points of view, I just want to add an important fact:
Kids will see a lot of adult behavior in media and around them
Kids will be exposed to a lot of input on behavior. The most important one will usually be of their parents. But they will also sometimes see things on TV, the internet, talk with other children or just see behavior of adults in public. All this will form their perception and idea of how to express affection and how adults should behave with each other. An answer mentioned "What happens if they copy you while playing house? That should give you a clear idea of where to draw the line." - most of kids this age will try a lot of inappropriate stuff. They have seen stuff on TV, or heard other kids talk about what they think adults do under the blankets and they will try stuff. And you will not stop this, by not kissing affectionately in front of them.
I think the best way to influence the behavior of your kids positively is to show a positive version of all behavior they are expected to see/encounter regularly as a kid in a modern society. They will see many forms of affection, so you should also be affectionate with your partner in front of them and make sure they connect affection with consensual, positive behavior, without a lot of shame.