In "Paradise Lost", when asked if the Sliders have families, Arturo replies, "We four are all the kin we have."
The scene where the three remaining Sliders eulogize Professor Arturo.
Rembrandt: I was glad to know you, Professor. You were truly unique. You could be cantankerous at times, but I know it was because you cared about us. And when we get home, I'm gonna write a song for you. Something classy. Something righteous. So people will never forget you.
Wade: I don't believe in good-byes, not really. I can't believe that everything we are, everything we've done, just disappears. I think our spirit...is like a river. It has to go somewhere. I know in my heart, I'll see you again.
Quinn: I never would have been the student I was without your guidance...and love. You taught me there are no limits to the imagination. You were a true adventurer, now you're the greatest adventurer of all time. Good-bye, Professor.
According to Arturo in "Slide Like An Egyptian," Quinn had a dream in which he was Arturo's son. Arturo then laments not having the courage to tell Quinn that he wished that were true.
"Season's Greedings" being a Christmas Episode naturally meant a lot of this. Notable is Arturo's storyline, in which he feverishly tries to reunite a mother and her baby (prompted by him knowing the pain of losing his own mother) and instilling some morals to children as Santa Claus.
In "The Dream Masters," when faced with the possibility Wade will be left comatose for the rest of her life, a guilty Rembrandt vows to stay behind and take care of her for the rest of his life.
In "Dragonslide," they are on a world where magic is real, and a magic spell accidently causes Rembrandt to fall in love with Wade. Later after the spell is broken and he finds out what happens, he admits to Wade that he may really love her. He tells her all he wants is to go home and be with the people he loves, and being with her he gets part of his dream. At the end of the episode they jump through the vortex arm in arm.
In "The Seer," Mallory has this talk with Mrs. Mallory:
"There is a still a small part of your Quinn inside me. And I think he wants you to know that, to him, you aren't just a stepmother. You raised him, loved him. For that reason, you are more his mother than any blood relative could be. He loves you very much."
Towards the end of "Last Days," when Rembrandt rejoins the group after spending most of the episode on his own.
"I couldn't face the end of the world without my friends."
During "Slidecage," Rembrandt is captured by the Kromaggs and befriends the commander's masked son, Kaldeen. Rembrandt later learns that Kaldeen is an orphaned human originally named Jules and was taken in by Kolitar as a child after a deadly raid that claimed his own son. As the two are about to part ways at the end of the episode:
During "In Dino Veritas," sometime after Quinn has gone missing:
Wade: I used to have the biggest crush on him. Did you know that? Now, after everything we've been through, I just really love him, y'know? Without condition. I'd give my life for him. Arturo: You know, I think all of us would. The first time I met him, I was giving a... a rather brilliant but very technical lecture to a bunch of very distinguished scientists. Suddenly, this... this tall, gangly first-year student gets up and asks an impertinent question. I was annoyed at him. About a week later, it suddenly occurred to me that quite possibly he was right. And then I was exceedingly annoyed at him! You have no idea, Miss Welles, the joy of being a teacher when at last you come across that rare and unique thing—that first-class mind. That boy is well! I'm sure he is! I can feel it in my bones.
In "Rules of the Game," a blinded Arturo tells Quinn, "Every teacher goes through life hoping just once he'll have a student like you."