The fact they he is in Canada likely trying to secure a WP isn’t ideal. When did he enter Canada? Has he had any childcare experience? How long has he been a social worker? Is he currently employed as a social worker? A social worker is a master program in Canada so taking a job as a nanny would be seen as purely to secure immigration. How old is your child? Are both parents working full-time and how old is the child? How much income does your family earn and do you live in a live in a city where housing is over 500k for example. If you make less than 150k it it difficult to afford a nanny given the cost of living in most of Canada. The cost of daycare has decreased so the cost of 1 child attending daycare would be significantly more affordable. If the child is 4 then they also will be attending school so also hard to justify paying a nanny’s salary versus paying for after school care. You would need to ask yourself whether you would be willing pay for a nanny if your brother was not an option. When people’s family get denied many do place their children in daycare which confirms that immigration is the primary goal. You should certainly try but also have a back-up plan like having your child’s name on a wait list for a daycare