This afternoon my parents visited me. It was all pretty normal until just before they left, they told me that my estranged grandfather apparently suddenly felt the need to donate a large gift of money to all his grandchildren. Then they handed me an envelope containing a considerable amount of money.
Apparently, he gave a set of these envelopes to my uncle, who then gave them to my parents, who then gave them to me and my siblings. I haven't spoken to my grandfather for years and neither have most of his other relatives (outside my uncle) for some family-related issues (which are a long story).
From what I heard (indirectly) the reason for this was apparently the death of his sister and seeing how much of a hassle inheritance law was. My uncle said there's no intention to guilt us into anything; he just wanted to get the money to us in an easier way.
I'm not a particularly outgoing or socially strong person, and my grandfather has a long history of being selfish and peculiar. It's not that I really dislike him, but he's often rather reclusive and I have a hard time maintaining good ties with my family even when those members make an effort. Obviously I feel that I should thank him for this gift, but I'm a bit stumped on how to go about it. What's an appropriate way to express thanks here?
(My grandfather lives within travelling distance, and I can get his current address through my parents. I don't think he's using a computer.)