Oh my ever-loving jesus. I love this book. I, like you, found it at my Gram's house when I was 11 or 12. It started my love of epic family novels. Included in that list are The Outlander Series, and "One Hundred Years of Solitude".
I also love Maeve Binchy's "Light a Penny Candle". However, I do think that "Light a Penny Candle" is the better of the two.