M.H.
Please dont try and figure this out. You cant. I figured out a long time ago, not and try to say what I think it "should" be. It will drive you crazy. All little people do things at different times. My kiddo walked early (according to "they", you know, "they say") However, she isnt talking according to what "they" say. These kids do things in their own time. Now, if your youngster were a year and not sitting up, go to the Pedi. My sister talked at one year of age...she taught my brother, who is a year older, to speak. You just cant predict the future. (unless you have a crystal ball, in that case, can we be friends!?!!)
You also absolutely cannot hold a baby too much. That has NOTHING to do with it. He will sit up when he's good and ready!!!
Good Luck and dont worry!!
Margaret :)