You may have a hard time adopting the children since both parents are still living and neither has terminated their rights to the children. In addition, you would need to serve the mother somehow to have her involved in the process, and with birth mother being in Kenya, that is a problem.
Another interesting facet is that to even apply for conservatorship (not quite being a parent, but many of the same rights and duties) you will need to serve bio mother.
The divorce itself should not involve the children since they are not your biological children, and not "children of the marriage." While his infidelity may play a part in the divorce and division of assets, it does not likely play a part in child-related issues.
Getting someone served in another country is hard, especially if that county is not part of the Hague Convention. I do not know if Kenya is or isn't. You are going to need to flesh this case out with a lawyer and understand what you are trying to do, with regard to the children, is not going to be cheap, but it will be worth it.
This answer is intended for informational and educational purposes only and should not be considered legal advice nor forming the attorney client relationship. This attorney is licensed in Texas.
I agree with Mr. Harding, and just want to add that it MIGHT be possible to establish some conservatorship rights with the children through a Suit Affecting Parent-Child Relationship. It is a long shot, but if the kids are worth the fight, it might be worth it to explore the possibility. Good luck.
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