Can I connect multiple accounts from the same platform to one brand? 

No, currently it's not possible to connect multiple accounts from one platform to the same brand. In case you are using multiple ad accounts or similar for one and the same brand the solution is to do as following:

As an example - let's say that you are using multiple accounts because the brand are marketing themselves in different countries and you have one account for each country for some of the platforms. In such case you will need to: 

1. Create one brand per individual country (name them so you know what country) 
2. Connect the account that you're using for each channel related to the specific brand + country 
   
   

Similar approach can be done based on other type of categorisations or similar. The most important part is that you apply naming on brand that reflects what accounts that you are connecting from each marketing platform you want to use when managing or reporting on campaigns.