Verse 21 should not be read without 22 as they form a logical set. Jacob uses the plural of "isles" to be able to include his people in a typical rather than unusual pattern of the Lord. There are other isles, therefore there are other locations where the Lord has led some of the house of Israel. Therefore this branch of Israel should understand that it is still part of the great plan, and still inheritors of the blessings and promises. This branch is not unusual, but a repetition of a pattern of the Lord.