poweraMany African families spend fortunes burying their dead
This article seems to establish that kinship leads to the failure of wage growth and ultimately wealth, people will hide their wages because people will ask for money. This seems like the issue rather is is that wealth accumulation in sub-saharan africa is limited to a small subset of population, I don't think this wealth tax by family members exists when you have a larger group of individuals making more money.
You can observe this in the US, and presumably in the rest of the world, when wealth is concentrated to individuals, your family will probably ask you for money. The difference is here, there is less income inequality and more people have the ability to make more money.
I do like the look into funeral culture, but I don't think this assumption that kinship and family-peity is the cause of the lack of economic mobilty.
Ghana's GINI index is only a couple points higher than the US (43 vs 41), and the same as Mexico.
I don't think wealth inequality explains this at all. But what rigid social institutions of any kind tend do is inhibit mobility. Moreover, kinship groups like this tend to lock-in relative wealth by lineage--the wealthiest family of a kin group from 3 generations ago will be much more likely (relative to other cultures) to be the wealthiest family 3 generations from now. Greater mobility means productivity increases faster, which raises absolute wealth for everybody even if relative wealth disparities across the entire population remain constant.