I regret the one and only time I sent an alien baby back to homeworld.
My alien male Sim (Evan) is married to a regular Sim (Vera) and they had two children, two boys. They decided to have one more child. They had a daughter. As soon as Vera came home from the hospital with the new baby, Evan was kidnapped by his own species and he became pregnant.
I panicked because they didn't have room for two new children, I already had to move their oldest teenage son to the basement. I love their house so much I didn't want to move and I didn't even find a suitable one from the gallery. I decided to send the alien child away.
I didn't really want to do it because I knew it would make me feel awful and I tried to think of how to expand the house so I could keep the fourth child, but the only solution would've been to get rid of their garden or Vera's space ship (she's an astronaut). Both of those are important to the game play, so I didn't want to do it.
When the baby (another girl) was born I quickly sent her back to homeworld and I instantly regretted it. I could've made another room in the basement and moved the other son in there too, so the girls would've had room in the upstairs. I guess I thought it was too harsh to make a child live in the basement. It was okay for a teenager, though, he has a nice room in there and he loves to have his privacy.
This family is one of my favorites and now I feel bad every time I play with them. I know Sims is just a game, but I get attached to my Sims and their lives.