When Garion learns Polgara's real age, he realizes she couldn't possibly be his aunt. But along the way, he learns how much she does love him, and begins to understand that they can still have their surrogate mother/child relationship, whether they share blood or not. And it turns out she's his great (great-great-add-a-few-hundred) aunt anyway. Belgarion is descended from her sister.
Vordai, the witch of the Drasnian fens, will only help Belgarath, Silk, and Garion get out of the fens if Belgarath gives the intelligent, otter-like fenlings the power of speech, so that humans will no longer view them as animals and stop trapping them for their fur. When one of the fenlings demonstrates his success by speaking the word "Mother" to Vordai, echoed by many other fenlings emerging from the swamp in excitement, the witch breaks down in tears. The reader may also, just from the touching impact of the moment. The fact that Belgarath does as Vordai asks out of sympathy for her lonely, sad life, rather than using his power to get the party out of the fens directly, just makes it better.
The coda to this in Guardians of the West: Garion, on his way to the shrine where the Mrin Prophet was kept to read the original scroll of the Codex, runs into the fenlings again, only to find out that Vordai has indeed passed on. The simple, childlike way the fenlings speak of her being "tired" and how they put flowers on her grave is heartbreaking, but also shows how much they really loved her.
Porenn taking care of Silk when he breaks down crying after revisiting some old family issues.
Mixed with Tearjerker, as Porenn makes it clear she's done this before, and knows exactly what to expect each time Silk visits his mother.
In Belgarath the Sorceror, after Beldin announces his desire for his own tower, his brothers start arguing over what kind of tower to build. Appalled at their fussing and arguing over the design, he demands to know why they are going to so much trouble, to which Aldur replies that it's because they all love him and want him to have a nice place to live. Beldin, who's been an outcast for much of his life and assumed that nobody would ever care about him, breaks down weeping.
The end of Polgara the Sorceress.
"I loved my father. It was as simple as that. I loved him in spite of his many flaws and bad habits. That stunning realization brought tears of happiness to my eyes as that love filled my heart."
The end of Seeress of Kell.
Then, with the God-light bathing their faces, the three friends started down from the snowy hilltop to view that miracle, which, though it is most commonplace, is a miracle nonetheless.
A sweet and rather humorous one: when Polgara marries the resurrected Durnik at the end of the first series, the Gods seem to imply that the condition for their relationship is that she give up her powers so that they can be equals, which she does without a second thought. Then, months later, it turns out that she still has her powers; the Gods made Durnik a sorceror instead.