especially when kids are at age when they are about to hit puberty,their hb levels should be kept as high as possible and ferritin as low as possible,so that they'll have no issues with fertility in future.
I think its a fair assumption, however fertility issues will not occur, its not a guarantee. Please read below excerpts from Northern California Comprehensive Thalassemia Center.
Causes of Reduced Fertility
Fertility is influenced by the ability of the female egg or male sperm to mature and be fertilized. In females, it is also influenced by sexual maturation and the ability of the uterus to carry a pregnancy to term. Delayed sexual maturation can preclude the ability to have biological children until puberty is reached and, for girls, menstruation has begun. Some women with beta thalassemia have primary amenorrhea (menstruation has never started). This must be corrected and menstruation initiated in order for such a woman to conceive and carry a pregnancy. The same is true for secondary amenorrhea, in which a woman who previously menstruated no longer does.
Prevention of reduced fertility
Reduced fertility in the individual with thalassemia is mainly attributable to iron overload in one or more of the organs or glands that contributes to egg or sperm development. In females, eggs in the ovary ripen in response to hormones released by the anterior pituitary gland. The pituitary receives signals to release (or stop releasing) these hormones from the hypothalamus, which in turn receives signals from the ovaries. In males, sperm is produced in the testes. Like the ovaries, the testes receive hormonal signals from the pituitary, which receives signals from the hypothalamus. Fertility can be reduced by iron overload in the pituitary gland. The damage that results prevents the release of pituitary hormones in response to signals from the hypothalamus. Iron overload can also occur in the hypothalamus. Infertility may result when iron overload in the ovaries or testes causes damage to the egg or sperm cells.
It seems that the best approach to trying to prevent reduced fertility or infertility is controlling iron levels. The body is unable to get rid of the excess iron it accumulates from chronic blood transfusions. Desferrioxamine (Desferal) helps to remove this excess iron. This medication is usually administered five to seven nights a week through a pump that slowly infuses the desferrioxamine beneath the skin over several hours. Studies suggest that effective use of desferrioxamine can lead to normal sexual maturation. Patients who do best are those that start treatment early, before iron levels become high, as measured by increased ferritin levels. Those that keep their iron levels low throughout treatment also seem to have a better chance at preserving their fertility. However, even those with very high ferritin levels over a long period of time can experience normal sexual maturation, although rarely. This is seemingly counter to the proven positive effects of desferrioxamine therapy. It is important to remember that ferritin values are not an absolute indication of body iron burden, as these values can be affected by other conditions, especially liver disease. The only positive method measuring iron deposition is a liver biopsy.