This can be a sensitive subject so please be advised, you need to have a few additional documents if you want a Brazil eVisa for your minor child. You, as a guardian or parent, must upload additional documents when you apply. You need to prepare a copy of the passport page and photos of both parents, as well as an authorization letter signed by both parents. If you travel with your child alone (e.g. divorced,) you are required to upload an authorization form from the other parent. If the other parent is deceased, you need to have a death certificate. Last but not least, if you have the sole custody of your child, you need to have a legal custody document. The point is that you need to prove that you do not take the child out of the country without the other parent knowing.