The Vardon family, in which both parents were deaf and their younger son was blind and autistic. Their older son was responsible for caring for all three of them. He was fourteen.
This was put into a very recent episode with the Stott family, whose mother had leukemia and was saved by bone marrow given by a guy that helped out on the project. Their house burned to the point of being unlivable due to the mother's illness. All of the things they did...one of the boys made her a "cancer dragon" that she keeps by her bedside so that it'd eat her cancer.
The Kadzis family. Dear God, the Kadzis family. The episode won an award for being "Most Touching" for a reason. (For those who didn't see it, the parents of the family had seven children, six of whom were special-needs orphans they adopted from China; one daughter was deaf and another was blind, although the others were doing better following surgeries and treatments. They petitioned for help when the father was diagnosed with stage-four brain cancer. Three days after the family moved into their new home, he died.)
The Piestewa family. Not ONLY is it the usual fix-up-a-nice-home-for-some-nice-people sentiment, but then you've got the fact that the Piestewa family consists of the parents and the children of Lori Piestewa, the first woman casualty of the war in Iraq and the first EVER female Native American killed in overseas combat in this country's history. And THEN add that in the fact that Lori Piestewa had been killed in the same ambush in which Jessia Lynch became a POW — and Jessica and Lori had been friends and made a pact to take care of each others' families, and so it was Jessica Lynch who nominated the Piestewa family for the show. And THEN add on the fact that the crew decided to not just build a new home for the Piestewas, they also constructed a new Veterans' center on a nearby Navajo reservation, got Sears to donate $300,000 worth of new clothes to all the other families on the reservation, and placed a memorial marker to Piestewa on nearby Piestewa Peak, which had been recently re-named in her honor. SO. MANY. TEARS.
The Imbriani family, whom apparently had not actually applied for the show. Instead, they were nominated by a lady named Nancy Avila, who had never even met them. It turns out that Brook Imbriani had donated blood and then bone marrow, that went on to save the life of a little girl who suffered from leukemia, named Esmeralda. The little girl's mother, Nancy, eager to find and meet the person who donated the bone marrow that saved her baby's life, asked the show to find this family and if they could fix their house. Made all the more amazing because Ty and the crew went to make the wake-up call to the Imbriani family without the Imbriani's even knowing about it, and you could see the surprise in their faces. They get the makeover, as the house did need repairing, but did not reveal the whole story to Brook and her family until they were seeing their new house. Ty then tells Brook that he knows she donated bone marrow, and then reveals who the bone marrow went to, and out comes Nancy with her daughter Esmeralda, and the emotion and tears just pour as the women hug, with Nancy thanking Brook for saving her daughter's life, calling Brook an angel.
The Walker family. The family's brilliant eleven year old boy hung himself because he couldn't put up with profuse and incessant bullying. They were unable to visit their third floor. It just held too many bad memories.
The Hill family. Because of the father's PTSD, he couldn't go see his son run track because of the noise.
In the series finale, the team built seven homes for seven families in Joplin. Two of the families, the Cogdill family and the Whitely family were neighbors before the tornado. Crystal Cogdill lost one of her sons. Crystal Whitely lost her son and one of her daughters. Thang Nquyen came to America after losing everything in Vietnam. Then, just before he retired, he lost his home again. Scott Ely and Natalie Gonzalez decided to get married after they survived the tornado. In a big surprise, they were granted a wedding at Walt Disney World. ABC even flew out Gonzalez's oldest son (who was away at college) to walk her down the aisle. Aww!
This entire series is comprised of alternating segments of Tear Jerker, Heartwarming Moments, and Funny Moments that seem to also be heartwarming. The result is that the mantra of this troper's family when watching this show has become "Awwww... *Sniffle* dammit..."