Thank you for your query.
I can understand your concern when you compare your children with other children. Let me at the outset inform you that every individual's height varies and cannot be compared with other children.
Your children are attaining puberty
and at this time you shall soon find them gaining height. So do not worry. Do not go after medicines claiming to increase the height. They may even harm the children. Just ensure they get a good nutritious diet and have daily exercise to keep themselves healthy.
I hope I have answered your query to your satisfaction.
Wishing your children all the best...