What is the War between two neighbors, which neighbors were born one and grew up as one, till a force made them virtual enemies?

One Nation divided along religious lines by a foreign force destroys the Nation leaving behind two enemies that are actually one. It is the same as two brothers separated on one Motherland by a foreign force and turned into virtual enemies; one boasts a global economic leader recognition and the other has an economy of debts it owes to another foreign power. The debt ridden Brother is jealous of his kin with global recognition that he constantly tries unsuccessfully to ruin using Terrorism from its soil. What should the Mother do in such a situation; doesn't a Mother see both brothers alike? If the two brothers join forces again, the one Nation will become a global powerhouse.