I don't know -- define "large" family. My DH only has him & his sister and that man inhales his food. So, basically is a family of 4 considered a large family?
I, on the other hand, come from a family of 5 and tend to talk throughout dinner so I'm the slow eater.
My oldest son INHALES his food as if he hasn't eaten ever -- no matter how much I tell him to slow down, it's like he has a hot date or something EVEN going out to eat & it's not like he's going to get to leave the table until we are all finished with the meal.
Of course, then my youngest son dawdles where EVERYONE is done with their food and he is still just slowly picking at his, so we have to encourage him to hurry up.
So, I think some of it may just be personality?
Edited to add: I just finished reading the thread and realized oldest DS sits next to DH at the dinner table while the youngest one sits next to me!!! Interesting. However, DD is a bit slow to eat (probably more in the normal range) and she also sits next to DH while my middle son sits next to me and I think he's in the middle for eating too -- funny thing is DD & DS9 sit next to each other!!
I also wondered if it was the youngest in the family that ate slowest -- I noticed in another post their youngest was the slow one, my youngest is the slow one & I realized I'm the baby of the family and out of the parents at the table, I'm the slow one. My DH is the oldest in his family.