Of course, everyone can do yoga ! And everyone should do yoga !!. As the scriptures say: "Vraddho, Ati Vraddho, Ball, Yuva Api". This means: "the old, the very old, children and the young - everyone should practice yoga." But according to age, interests &needs differ slightly. This is especially true about physical practices. The mastery of the teacher is to create a sequence that will fill everyone with joy, suits their interest and at the same time should be beneficial for all. Very few teachers accept this challenge.
But if your goal is all-round development (not limited to physical practice), then it is better to have people of different ages in the group. We recommend family yoga when children, parents and grandparents can practice together. No one feels lonely, no one needs to wait for someone else to take care of themselves. Although the quality of physical practice can be reduced by 10-15%, but if to evaluate effect on whole life in integrity, the result is 150% better than in a regular lesson.
Pregnant women should attend special classes, after consulting with the teacher. And yes, they should also practice yoga. In fact, for them, yoga is even more important than for other people, because each mother is directly responsible for the physical and spiritual development of two people and indirectly - many others. There is a detailed study of what practices should be done before conception, during pregnancy, after childbirth, during feeding, both for the proper development of the child and for the benefit of the mother.