my son can sitting straight well right now, may be my mother let him sit on the walker very early( around 3.5 months),therefore, he could sit on the sofa with me to watch TV, but he seldem climb himself
My baby drops from 50 to 25 to 10 percentile. Only 15 lbs. May be weight is the reason.
Coz she start to
-turn over at 4.5 month
-sit at 5 month
-crawl (very fast) at 6 month
-stand at 6.5 month (she is trying free hand stand now)