OK, that pic made me wonder how the penguins got it done, adoption not being so common among animals (with notable exceptions here and there). Turns out it's a cute story of a couple of male penguins in a zoo that were given an extra egg and they worked to hatch it together- actual true story. I don't have little kids (daughter is 29) so haven't been around children's literature in a while.
Seems pretty harmless but apparently has been the subject of a lot of controversy..
https://en.wikipedia.org/wiki/And_Tango_Makes_Three