My DS is almost six months old and is very lively and mobile. He loves to bounce up and down Strong legs) and roll all over the place. I am trying to encourage him to sit. He will sit for small amounts of time leaning back against me, or on our bed, but really doesn't like it. He is quite a slim baby (9th centile) and also has a misaligned bottom cleft (really don't know what else to call it, other than wonky bum crack!) and although his hip scan showed up no problems, he doesn't like to seem to bend the way that is required for sitting. I would say his hips seem "tight". Has anyone else any experience of this? Is it something I ought to be discussing with the HV/GP? He is my first, so it's probable I am being PFB about this, but by the same token, I don't want to overlook something that could be more complicated....help!