Ummmmm looks like he may be in motion early like his sister (who was walking by 9 months. The joke was that she was ready to by 4 months, all the moms in baby group were waiting to see her take off any day.)
She did a lot of early sit ups and always wanted to be standing (we had to hold her up. We joked it was the only accepted position and she'd do a little warning squawk if you tried to hold her like a baby)