Hi hansT,
Smart radio buttons can be grouped via setting their groupName property. In your case 6 buttons in 2 separated groups can be initialized by the following code:

    <smart-radio-button group-name="groupA">Option 1(group A)</smart-radio-button>
    <smart-radio-button group-name="groupA">Option 2(group A)</smart-radio-button>
    <smart-radio-button group-name="groupA">Option 3(group A)</smart-radio-button>
    <smart-radio-button group-name="groupB">Option 1(group B)</smart-radio-button>
    <smart-radio-button group-name="groupB">Option 2(group B)</smart-radio-button>
    <smart-radio-button group-name="groupB">Option 3(group B)</smart-radio-button>

Best Regards,
Ivailo Ivanov
Smart HTML Elements Team
https://www.htmlelements.com