One of the largest assets of a family is the Matrimonial Home or the house that the family resides in. Often times, third parties such as, parents, siblings, extended families and friends of a couple have interest in the home by way of their name on the title, their monies being invested in the down payment or monthly upkeep of the house, or otherwise.
In such circumstances, if the couple separates, third parties may become part of the family law proceeding as a result of their interest in the home. Even if third parties wish to deal with their interest in the home though a civil suit, their claims may only be heard in the family law proceeding. A similar viewpoint was held by the courts in the recent Superior Court decision, Malkov v. Stovichek-Malkov.
https://www.canlii.org/en/on/onsc/doc/2015/2015onsc4836/2015onsc4836.html