Salaams... fasting is an individual duty as Allah (swt) has obliged EVERY Muslim who is of age and abled body and mind to fast:
“O you who believe! fasting has been prescribed for you, as it was prescribed for those before you, so that you may attain Taqwa (piety). [2:184]
Muhammad (saw) said: “Whenever you sight the new moon (of the month of Ramadhan) observe fast, and when you sight it (the new moon of Shawwal) break it, and if the sky is cloudy for you, then observe fast for thirty days”. [Muslim]
Those who are exempt have to make up their missed fasts or pay kaffara for each fast missed. In previous Q&A's (http://answers.ahadith.co.uk/509/fasting-exempted-when-person-ill-later-has-make-now-question) the exemptions to fasting have been given with explanations.
And Allah knows best... your brother in Islam