2nd time visit to Germany

[sudasarav]

My parents visited my brother in Germany last year and stayed for 3mnths May-Jul. Now they are planning to go again this year in March for his wife's delivery. How long should they wait b4 applying for visa? Is there a min period between trips for tourism to the same country. PS: They had schengen visa from Germany, main stay was Germany and visited a few other schengen countries too. Also I would also like to know should u leave from the same country in which u entered ie if I entered Germany can I leave from another Schengen country or do I have to go back to Germany and then come back to India

Thanks
S