We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
As an ironborn I know you can raid someone who has one and if you sack the city that they're located in you can steal theirs but if they're leading an army you're out of luck to my knowledge.
You can also marry someone who has one then your kids should inherit it. Not 100% of the time, I know that some of them go to a dynasty member not the child, for example I married Jon Snow's bastard daughter who had Longclaw and on her death it passed to Sansa Stark as the last remaining Stark rather than her actual heir. (Bran, Arya and Rickon never revealed themselves)