DS is 21 months and not really talking. He is third child in the family, siblings 3 and 12.
He says perhaps 6-10 words - no, Maaa (mummy), gah (car), more, door, meee (when asked eg who wants lunch?), shoos, bye, and occasionally chiz (cheese), and others occasionally as a one off but not repeated.
He follows instructions, knows his name, like songs although doesn't really join in, seems quite cheery, and although he has the occasional tantrum when it's obvious he just can't communicate his needs, he's generally not agitated about much. He's affectionate and friendly. But he seems a long way behind on speech milestones - nowhere near sentences, making himself understood through words, etc.
He has a Spanish nanny and understands Spanish words, although doesn't use those either. He spends most of his time with another little boy about a month older, whose language is much better, and his big sister, when not with us.
When should we start worrying? Obviously I already have a bit, but this could just be paranoia!