Free goods based on product hierarchy

Dear all,

We have a requirement to issue free goods based on product hierarchy for example there are 2 line items in sale order which belongs to same product hierarchy, individually not qualify for free goods but when the quantities of both the line items added qualify for free goods.

Does any one already implemented such logic if yes, can you please guide me as how we can achieve it.

Is it possible to do the enhancement to achieve it?

Thank you in advance for you reply.

Regards,

Ali