Rivalries and feuds between tribes

[Hakim Khan Urgonai]

How prevalent are such rivalries and what causes them? Which tribes are feuding with others currently and what is the cause of it?
Can two Pashtuns from feuding tribes be friends/freindly towards each other?

My tribe (Kharoti) is said to rivals of Sulemankhel and at war with Wazirs, but I have many Wazir friends and relatives (from my tribe) in Waziristan.

[Hakim Khan Urgonai]

Any geniuses willing to comment?