The person who passed away is your great-great grandfather’s cousin brother’s wife. That’s quite distant in terms of relationship, and she’s not in your direct lineage. She’s not your grandmother or great-grandmother or even part of the main family tree you descend from.
In our Tamil Brahmin customs, theetu is usually observed only for close blood relatives—parents, siblings, children, grandparents, or anyone from whom you directly descend. Or if you’re someone who actually took part in the cremation or the final rites. In this case, since she’s a relative by marriage in a side branch of the family, there’s no need for you or your father to observe any theetu.
You don’t have to avoid festivals or skip functions for a year. There’s no ritual restriction that applies here. Of course, some families have their own traditional ways of showing respect for distant relatives—like observing silence or avoiding something for a day. That’s more out of courtesy than actual ritual requirement. If your family does that kind of thing, you can decide based on that.
But strictly speaking, as per our customs and rules, you’re not required to follow any theetu here. You and your father can continue all regular rituals, poojas, and functions as usual. If there’s still confusion, a quick word with your family elders might help clear up if any specific tradition is followed in your household.
