I have been using Indo maid to take care of my elder daughter. Same as your case, my son was born when my daughter was going to be 2 years old.
We had considered the previous maid hired by my relative. At the end, my existing Indo maid referred her cousin to us. Her cousin was already working in HK taking care of a toddler that time. We employed after she had finished her contract with her previous employer.
There are good points and bad points to hire 2 maids who are relatives. However, I think good points are more than bad points. Even when they have arguments, they will make it up at the end. They are relatives and will not hate each other forever. Bad points are that they are talking talking and having fun at home --- I guess. Also when hire 2 maids, they will become lazy. They are too used to share duties. They also like to quickly do the household work and have the spare time to cook their own food and chi-chat. They will not think of what else they can do to make the home cleaner when they have spare time.