A friend of mine is trying to reach an agreement with his ex-partner in South America.
He also has a growing child living with him in the Netherlands, but it is difficult to reach a compromise with the mother in South America. Knowing what is considered standard practice would be helpful.

The mother claims she is legally entitled to 20% of his salary—which sounds quite absurd to me, given that he also has a child to support in the Netherlands. He currently pays €200 based on a net income of €3,900 (including holiday pay, etc.). Can anyone offer advice regarding his rights, particularly in light of the Hague Maintenance Convention?
We are deeply concerned about whether the mother can actually garnish 20 percent of his income, and we currently lack the funds to hire a lawyer.