[BlackRedGold25]

Originally Posted by Makarov

In order for a distinction (or differential treatment) to be discriminatory, it must be made on the basis of one of a number of "enumerated or analagous grounds" or personal characteristics. There are nine grounds enumerated in the text of Section 15 of the Charter: race, national or ethnic origin, colour, religion, sex, age or mental or physical disability. A personal characteristic can also be analagous if it is immutable or cannot be changed or can only be changed at excessive cost (for example, sexual orientation.)

In the case of not being permitted to marry one's sibling, that distinction is not based on either an enumerated or analagous personal characteristic, and therefore cannot constitute discrimination.

I fail to see how a family relationship is not immutable. You cannot change who you are related to.