My 8 month old is not good at sitting. She can sit unassisted for a few seconds before losing balance, but most of the time she has no interest and wont try to sit (intentionally throwing herself back, wriggling down if being held, going rigid if being put down in sitting position). All the other babies her age we know seem to be excellent sitters so although I know it isn't that unusual it feels like she's behind and can't interact the same way (e.g a recent trip to beach the other babies sat nicely while mine rolled around and ate sand) Any tips to help with sitting? She can roll very well and is is it starting to commando crawl a bit (but mostly rolls still). Do play nests actually help?