If you give them your hearth secret they can kin you.
If they are kin they can get into party with you.
If they click on the coloured box that represents you under their own portrait in top left they will begin walking in a straight line towards where you are. (If you go into a house or a mine it stops working until you come out again.) My friend just did this. He had to make three boats and to travel for about five hours to get to me.
In this way you can find each other.
Your best bet however is to have the first person give their hearth secret to the others and have them tell that secret to Mr. Holmes while they are still in the character creation room. Then they will spawn beside your hearth fire.