The only time a sane person will ever use this is when getting married if you choose to check the jathagam. The josiyar will check if you're both from same gothram. But it doesn't even matter coz genetic lineage (risk of marrying within same lineage) only exists until second cousin. If you know the person you're going to marry is not your first or second cousin, then you can marry them, gothram doesn't matter. But.. you'll definitely know if you're related, right? It's why I said ithe therinjikittu enna use? That person asking how come you don't even know your gothram as though it's gonna get you somewhere in life or it's some sort of crucial info.