Yeah, it was kind of a bad joke and just sounds weird. My reasoning behind the answer was the following:

• Your own children are probably one of the things you love the most in this world, it is rare for someone to hate their child. (therefore they are most loved as requested by the question)
• Conceiving, gestating and giving birth is an effort from the mother, and therefore the offspring can be called the fruits of her work. (and are thus fruit as requested by the question) I thought that giving this answer would be unexpected in the context of this question, but make sense with the reasoning given (“the fruits of a mother’s labour”). I considered that to be a bit funny.
• Labour is a synonym of work, but can also refer to the last stage of pregnancy. Depending on the meaning the word “labour” takes, the sentence’s meaning does change, but both interpretations still make sense in the context of the answer. I thought that that double meaning adds a bit more to the fun mentioned in the previous point.