Full-time servants age, and so do their parents. When parents are Witnesses, likely their fondest wish is for their children to stay in their assignments. ( 3 John 4 ) Of course, if their parents need care, full-time servants will do all they can and will come to help them as often as possible. Still, those back home may help those in the full-time ministry by being ready to provide care if aging parents need assistance. Bear in mind that full-time servants have significant responsibilities in the most important work the world has ever known.
Hmmm, that reminds me of a Scripture:
And he said to them, "You have a fine way of rejecting the commandment of God in order to establish your tradition! For Moses said, 'Honor your father and your mother'; and, 'Whoever reviles father or mother must surely die.'But you say, 'If a man tells his father or his mother, "Whatever you would have gained from me is Corban"' (that is, given to God)—then you no longer permit him to do anything for his father or mother, thus making void the word of God by your tradition that you have handed down. And many such things you do." (Mar 7:9-13)