Is it possible in both families-the brother?s and the sister?s family to have a baby with trisomy 21? What needs to be done and is it possible to give birth to a healthy child in such a case? So the first generation and the second (the brother and the sister mentioned above) are completely healthy (not carriers also). The brother has 3 kids: healthy male and female and affected daughter. The sister has twins-girls (dyzigotic) who are affected.