I have only found evidence that contributes to the opposite (Kahnemann), but I believe that it depends on the measurement, so I would like to include more references in my research.
Angeles, L. (2010). Children and life satisfaction. Journal of happiness Studies, 11(4), 523-538.
Kohler, H. P., Behrman, J. R., & Skytthe, A. (2005). Partner+ Children= Happiness? The Effects of Partnerships and Fertility on Well‐Being. Population and development review, 31(3), 407-445.
Nelson, S. K., Kushlev, K., English, T., Dunn, E. W., & Lyubomirsky, S. (2013). In defense of parenthood children are associated with more joy than misery. Psychological science, 24(1), 3-10.
Wikipaedia? In the US a wikipaedia citation is not even acceptable from students.
My anecdotal experience has proven just the opposite, but grand children, that is different. There is an old Jewish proverb that: "Grandchildren are God's reward for allowing your children to live." There is a reason one of the ten commandments is honor thy father and mother. I would think any mixed evidence is the result of different experiences. I know that as time passes my wife and I find more people openly discussing the true nature of the struggles of raising children. Any cultural differences may reflect an unwillingness to speak openly about children in certain cultures and even in the US in the past. Sorry if this is not formal but studies like this are based on real life but lose the reality in the averages. Good luck.
Children may be a source of happiness or unhappiness. If the nature of children is positive, it leads to happiness. If the nature is negative, it leads to unhappiness. When a married person has a child, he or she becomes a father/mother, an additional role. Generally to become a mother or a father is an achievement in one’s life. Hence, to have children causes happiness or to enhance happiness (eudaimonic). As far as the present moment is concerned, when a child gives love to the parents, allows to be loved, and behaves lovely hedonic happiness of the parents will get increased. When children become high performers or great personnel who give an immense contribution to the respective organizations and the society, global satisfaction of the parents will get increased significantly. There is a saying in our society that to be a great man, one must have three things: to write a book, to plant a tree, and to raise a child. The above are some of my reflections. I have attached a very interesting article written by Prof. Manfred Varies. Please refer to page 8 which contains something useful for you to enrich your rationale for the hypothesis.