@Pokari At first, the father made the Laika android as a reincarnation of his son and begged him not to "die on him again". He wanted his son back, but as the story continues you can notice that he cares for the android. The fact that the first Laika android making a twin didn't cross the father's mind hints that he would rather try to stop the lab from taking him away rather than just make another one before the lab staff can kick him out. He goes as far as remembering the twin who was supposed to be the "sacrifice" for the space program as another son of his when he returns from space.
The androids, though at first meant as someone's replacement, ended up becoming irreplaceable themselves, even if it's not outright told to us. In turn, their father is irreplaceable to them, even when they essentially murder themselves by erasing all their memories. While the first Laika had bonds with the rest of the family the second only had a faint memory of his father left, as he points out that the rest of the family doesn't matter much to him. What I took from it is that they may take someone else's role, but not be someone else.