My maternal uncle is inviting me to a wedding at Canada. So should I answer this question yes or no. The definition of family member is something different on the website.
You can answer 'Yes' even though the definition of 'Family member' as per CIC does not include uncles/aunts/cousins.
If possible do establish how you are related to your uncle i..e proof of relationship by submitting the birth certificates of your mom and her brother (same parents)