It is possible that the two are related. Sinus congestion is happens when the sinus drainage system of ducts gets clogged up or closed off. The normal sinus mucus that would other wise be able to drain normally gets stuck in the sinus and begins to brew an infection. Sometimes when people develop an upper respiratory tract infection (such as a common cold), the nose becomes inflamed and those sinus ducts get closed off. A few days later the sinus infection comes along. In addition to the nose becoming inflamed, the upper respiratory tract infection can cause secretions to drip down to the back of the throat (nasal drip). This can cause irritation of the throat and cause a cough. Thus you associating the cough and the sinus infection (both caused by the upper respiratory tract infection) may be correct.
The best way for you to avoid this is to protect yourself against those that are sick (especially kids). Make sure to eat healthy and get plenty of sleep to make sure you don't get run down. This can effect the immune systems function. Also, you can see a primary care physician
such as a family doctor
when you start feeling symptoms especially when you get the sinus infections. Good luck.