In France, the household income is taxed if the relationship is official (not necessarily marriage, you have free, fast alternatives). You'll be taxed the same

In France, the household income is taxed if the relationship is official (not necessarily marriage, you have free, fast alternatives). You'll be taxed the same if both earn 30k or if only one earn 60k. If I take old and rounded references, in both cases, you'll be taxed 10% of what your household earn above 18k,and 30% above 48k. With a child, 10% above 22.5k and that's it (data from a few years ago, the brackets start a bit higher now). Basically, one adult count as 1 part, a child count as .5 (except the third who count as 1 whole part do not ask me why), you take total income and divide it by the number of part, and check where it lands in the tax brackets.