“The leading case on adding parties is Children’s Aid Society of London and Middlesex v. H.(S.), 2002 CanLII 46218 (ON SC). In that case, Justice Grant Campbell stated, at paragraph 22:
[22] Since the court’s discretion remains the same under the current rule, I am satisfied that the principles used to add grandparents under the former rules continue to apply. In summary, then, I find that I must consider the following principles before adding a party to a child protection hearing:
| (i) | whether the addition of the party is in the best interests of the child, | |
| (ii) | whether the addition of the party will delay or prolong proceedings unduly, | |
| (iii) | whether the addition of the party is necessary to determine the issues, and | |
| (iv) | whether the additional party is capable of putting forward a plan that is in the best interests of the child. |
In addition to these four factors, Justice Campbell stated, at paragraph 24:
[24] Consequently, in addition to the foregoing list of principles, I must also consider whether the person seeking to be added as a party has a legal interest in the proceedings.
At paragraph 25, Justice Campbell went on to state:
[25] “Legal interest” is defined in Black’s Law Dictionary, 7th ed., (St. Paul, Minn.: West Group, 1999) as “[a]n interest recognized by law, such as legal title.” In child protection proceedings, an interest recognized by law occurs when a court has the opportunity to make an order for or against a person in relation to the child. For example, subsection 57(1) of the Child and Family Services Act enumerates the types of orders that a court must make where a child is found to be in need of protection. Each of the possible orders creates a legal interest in so far as the placement of the child is concerned. Paragraph 1 of subsection 57(1) creates a legal interest for “a parent or other person”, paragraph 2 of subsection 57(1) creates a legal interest for the “society” and paragraph 3 of subsection 57(1) creates a legal interest for “the Crown”. The parent or other person, the society and the Crown all have a legal interest in the proceedings because an order for the placement of the child can be made for or against them.
In A.M. v. Valoris Pour Enfants et Adultes de Prescott-Russell, 2017 ONCA 601 (CanLII), the Court of Appeal stated, at paragraph 24:
[24] It is not necessary for all factors [in H.(S.), supra] to favour the person seeking party status for the court to add him or her.
Accordingly, what this court takes from all of the foregoing is that these are the five considerations the court must examine in deciding, on balance, whether it would be appropriate to add the paternal grandparents as parties.”
Children’s Aid Society of Toronto v. M.S., 2018 ONCJ 14 (CanLII) at 28-32