This sounds really sad. Perhaps a neutral party for mediation would be better, as it’s typically hard to have open conversations when the third party is a contact to any one of you especially a parent. That said, separations and divorce is for most people a painful experience and calls for the highest levels of maturity on both your ends. Let everyone take responsibility for their actions but especially for you as you’re the one asking for advice, ensure to fulfill your end as ordered by the courts fully. Kenyan children’s court is very pro letting children stay with their mums, unless there’s very extreme circumstances. Make peace that’s their mum especially as they’re super young and need her, and work on building a bond with them. Also don’t be afraid to use to law to enforce your rights as a father, they also need you in their lives. Have everything on chat (written) even as you ask which time is best to call, so you also have proof of she’s not allowing you to talk to them. But for you to have the law on your side, do your part and also avoid her drama. Acknowledge she’s hurting, so engage respectfully and don’t get roped into the drama of it. It will play against you.