When reading to your LO, how well do they actually sit still and listen to the story?

I don't think my kids sit still very well and listen to stories as well as they should, more so my 3.5 year old since she's older. I'm not sure if it's because I am trying to read to both of them and they are just overly excited but they are all over the place and only half listening. The stories are usually pretty short too (board books or early readers) so it's not an attention span thing, I don't think. I usually end up cutting it short because I'm eventually trying to read over them, and that gets old.

Is there a way to get them to both sit and listen to at least one short story, or is that asking too much with their ages?