Site contributor icy780 has shared an excellent bass tab for B.B.B.F.F., including the reprise. He always does great work with his bass resources, so you should take a look!
The tab is here. Break out your bass and play along with this sweet sibling song. You can also visit icy780's Youtube channel. If you want to find icy780's other music resources, look on the music pages or use the newspost search feature (scroll down to the bottom of the page).