Whether or not literal piracy, corruption, theft and illegal downloading are pandemic in a country, most countries in Africa have a law recognize copyright (The situation with Eritrea is unclear: this document for the Ministry of Foreign Affairs that there may be some copyright protection, or laws in the works). Without knowing which country you're speaking of, it's impossible to be specific about possible consequences.
The first question would be whether using a VPN to access content outside of the US is a violation of Netflix (US) terms of service. The TOS states
You may view Netflix content primarily within the country in which you
have established your account and only in geographic locations where
we offer our service and have licensed such content. The content that
may be available to watch will vary by geographic location and will
change from time to time.
and just before that,
The Netflix service and any content viewed through our service are for
your personal and non-commercial use only and may not be shared with
individuals beyond your household.
So if you are watching content in Tanzania that is not licensed for Tanzania, that is a violation of the TOS. Additionally, "household" does not mean "any relative", so arguably any sharing of the account between siblings who live in different countries is a violation of the TOS. The fact that your brother is paying doesn't matter, nor does his citizenship matter. What does matter the most, to them, is that they have to license content from others, and the copyright holders may well impose prohibitions on distributing content outside a particular geographical zone. So they may have permission to distribute a film only in the US, and they are liable if the film is also distributed outside the US.
Because your brother has allowed you to access this content, they might terminate his account. They might also take you to court for copyright infringement, since any watching / downloading of video requires copying, and all copying requires permission (granted under the terms of service). You do not have any permission to watch stuff on Netflix. If they sue you in Delaware, they would have to get the judgment enforced in Tanzania (picking a hypothetical country), so the question is whether Tanzania would enforce infringement judgments. Or, they could sue you in Tanzania (since Netflix has actual presence in most countries).
It is impossible to know in advance whether Netflix would actually sue a person for illegally accessing content with a VPN, rather than just thwarting your attempt. They have reportedly developed the world's 2nd-best VPN-detection technology, just behind the PRC.