A lot of my sexual experience was me and my sister having sex almost every day when I was 10 and she was 9, for about 3-4 years.
Our dad kept watching porn when we lived with our grandparents and had to share the same room. He watched it in the middle of the night and I'd watch and sometimes my sister. At that time, it was just dry humping under the blankets.
When we finally moved to an apartment, we shared the same room and parents room was far from ours (image)
We just had as much fun as we can. The bed was too creaky and we almost got caught one time, so we had to throw blankets on the floor and do it there. There were even few times we had sex in the bathtub in the middle of the night and use the shower to hide our voices.
Eventually we grew out of it after middle school when my sister got her first boyfriend and I just started masturbating.