Hi Vladimir,
Thank you for your update.
The GetTableControl method and TableDescriptor property used to create the relation in ChildTable. If you need RelationMaster details in the UniformChild relation table, then please try using RelationKind and RelationKey property in GridRelationDescriptor to achieve this behavior.
Please refer the sample in below link.
http://files.syncfusion.com/support/samples/Grid.Windows/Forums/Relation.zipPlease let me know if it helps.
Regards,
Lingaraj S.