Relationships - One to Many

Hi,

I've had a search and can't seem to find the answer so I thought I'd see what people think.

I'm trying to sort out relationships and I have a one to many but can only seem to do many to many.

I've got a collection of 'Brands', and a collection of 'Products', I've got a relationship where they can pick the brand, but they can pick multiple brands using the type of text. I only want them to be able to select one brand.

Just to add to that 'Brands' can have many 'Types', but a Products can only have one Type, but obviously that type can only be selected once the Brand has been. I can't seem to work out how to have one perch:content be dependant on another?

Thanks for taking the time to read and hopefully someone can help me out :)

Chris.