I have own kingdom, and, at first, I was at war with Qohor. After a copuple of battles I've captured an enemy lord. When the chat with him ended, aka "I'm at your mercy". Another kingdom instantly declared war against me (Norvos).

-Maybe they were friends, or something, hence the declaration. - I've thought to myself.

Yep, I was wrong. The second captured lord gave me instant war with 5 another kingdoms (Ironborn, Lys, Pentos, Tyrosh, Lorath). Another captured lord resulted in a war declaration with multiple kingdoms too.

Tl;dr Capturing a lord triggers instant declarations of war with random kingdoms

Second bug (?) - it is kinda annoying, don't know if it is a bug, or intended. I gave fiefs to some of my companions, making them lords (and I did not have any "normal" lords in my kingdom, I was alone and in need of quick vassals, because I was at war with 2 kingdoms). Since then EVERY lord I encounter gives me -2 to relations with them, saying something like "I heard you gave X to >insert companion name<. Watch out, blah blah blah". No matter if I speak with a former companion lord, a lord from my kingdom, or a lord from other kingdoms I've never met before - they all instantly give -2 to relations with them.

tl;dr Making companion a lord triggers -2 to reputation with every lord you encounter and talk to.