With a second baby you can’t help compare their development with your first child. Russell has been very early to crawl having mastered it at just 7 months old whereas Penny took much longer. He can’t yet sit up, however, when Penny could at this age. One thing he is really behind on is teeth. At 8 months old there have been no signs of teeth until today when the first one started to poke through. His sister had at least 6 six by this stage, proving that all babies are very different.