Justin Timberlake is expressing his love for Jessica Biel! The 40-year-old singer took to Instagram on Wednesday to celebrate his wife's 39th birthday by sharing pics of them together throughout the years.«Happy Birthday to my favorite person in the world,» Timberlake began his tribute, before going on to call Biel «the strongest, funniest, best, brightest and most beautiful mom/partner/BOSS there is.»Timberlake, with whom Biel shares sons Silas, 5, Phineas, 1, continued his post by writing,