If you had your first child in your early thirties, it is better to have the second baby with a gap of just two years. There is a little envy or jealousy in the first child because this emotion appears only at about twenty months, and the first-born cannot yet think clearly about the new baby. You will also spend a lot of time with the first-born as he is still very much dependent on you.
This kind of jealousy is often seen in the first-born. After the second baby is born the mother has to attend the newborn; and the first-born feels that his mother has stopped loving him and loves only the new baby. He starts hating the baby and keeps inventing ways to get rid of the new child so that the mother will start loving him as before. This feeling is very natural and also very powerful.