My youngest boy sat up later and he started walking at 13 months (which is 3 months later than my oldest)... It seems like it took forever but he's a completely normal and healthy 3 yr old.

Some babies are a little late my daughter was late sitting up and late walking but she's fine

My first son didn't sit up until 7 months and my friends daughter didn't sit up until closer to 9 months. It's a little different for every kid but ask your pediatrician just to be sure. Does baby sit up with the help of a boppy or a chair/high chair?