Take a white tulip and click on Sparrowtail. Click on her again and she will ask you to talk with Milkywillow. Get out of the den and click on the sandy entrance. Go right and also press x to drop the white tulip. You'll see a grey tom beside 2 stones. Go right again and you'll see a yellow she-cat resting. Click on her. After that, go left and click on the yellow arrow. Go left again and go to the right hand side corner den. Talk to Sparrowtail. Again go to the yellow she-cat resting and talk to her. This time, go right and you'll see a grey she-cat. Then go again right and you'll meet a yellow tom. Talk to him. Now go further right till you reach two grey and brown cats. One is a tom and the other is a she-cat. Now just go one more time to the right and click a yellow arrow. Go left till you reach Sunnygaze, Bumblestripe and Sparrowtail. Click on Sparrowtail. Now you finally get the "Generational Bond" achievement. You can talk to Bumblestripe to hear about how Sunnygaze and Bumblestripe found FallenClan. Thanks for asking!