Can I help with seasonal quest?

Hello,

I have a seasonal character 45-ish level and have completed the seasonal quests up to somewhere I don't really know. My brother started playing d4 and skipped campaign but the first quest about the house of Lockhart or whatever the name is he entered alone. Is there a way for me to have access to his quests?

I know that in the campaign the state of the sanctuary is that of the team leader. Is it the same logic with seasonal chars? So if he invited me and is the party leader will I have access to the quests?

Thank you very much!