Any time Sandy or Kirsten leap to Ryan's defence. Especially Kirsten, given her initial opposition to taking him in. One such occasion is in Season 2 when Caleb accuses Ryan of only wanting the Cohens' money:
Kirsten: You are way out of line. He has lived with us for two years now and in that time he has become a brother to Seth and a son to me and Sandy.
Any time there is any kind of show of love between the Cohens and Ryan. Kirsten going to rehab and Ryan's "I don't want to see that happen again to someone I love." Seth half-carrying Ryan to the hospital.
At the beginning of Season 2, Kirsten tearfully hugging both Seth and Ryan after they return and calling them "my boys." A far cry from the bitch who earlier declared "I don't want this kid in my house anymore" (referring to Ryan.)
The comic scene in "The Avengers"
Seth cleaning urinals to get Summer and her boyfriend Zach tickets to see a band that she liked.