Thanks very much for now.
It's also good that your son is being seen by a speech therapist. What does she think the cause of the problem is? Does she tell you that he is making acceptable progress, or does she feel that he should be improving at a more rapid rate? You can ask your pediatrician to refer you to an early intervention program that will help determine whether there are any identifiable reasons for the language delays.
Children do not all speak at the same time, but there are definite periods during which certain sounds and combinations of sounds should be produced. Your daughter should be seen by a specialist in speech and language pathology. Has the woman working with your son taken a look at your little girl? Are the parts of her mouth and throat necessary for speech physically intact and functional? Has anyone checked to see if your daughter is physically capable of making sounds? Does she "babble" and make baby sounds, or is she totally silent? You should be aware that some children have what is called "developmental apraxia." This is the name of a condition in which the child is unable to move the muscles involved in speech.
You can ask your local school to do an evaluation of your son and your daughter when she turns three. If you haven't done so, you should take both kids to a speech and language clinic at a children's hospital. They will have the latest equipment and more experience with lots of children with speech and language delays. The speech-language pathologists and neurologists there can also help you determine whether any other conditions might be causing the language delays.
In addition to normal variation in the development of language, there are some other, less serious explanations for speech delays. Some children in big families don't talk a lot because they don't really have to. Older brothers and sisters (or even the kids in a daycare center) may be hovering over them, doing all the talking for them. Sometimes adults give things to children too quickly, and don't give them a chance to ask for things. You should know, too, that gifted children often don't talk when they are little and then at age three or even four start talking in full sentences like "little adults."
Let's hope that your children are just showing normal variations in their ability to speak, but it's important to know for sure, since early intervention for speech and language problems is critical, and can be very effective. I hope these suggestions help. Let us know.